Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
  Case Tag  
Price  
Sales  
Tax %  
Raw Total  
Incl. Sales Tax  
Rounded  
to Penny  
Rounded  
to Nickel  
Rounded  
to Dime  
  Purchase #1 $204.75   9.205%   $223.5972   $223.60   $223.60   $223.60  
  Purchase #2 $233.57   12.699%   $263.2311   $263.23   $263.25   $263.20  
  Purchase #3 $110.85   7.372%   $119.0219   $119.02   $119.00   $119.00  
  Purchase #4 $162.27   9.607%   $177.8593   $177.86   $177.85   $177.90  
  Purchase #5 $248.30   13.449%   $281.6939   $281.69   $281.70   $281.70  
  Purchase #6 $208.47   11.780%   $233.0278   $233.03   $233.05   $233.00  
  Purchase #7 $184.29   5.562%   $194.5402   $194.54   $194.55   $194.50  
  7 purchase totals = $1,352.50       $1,492.9714   $1,492.97   $1,493.00   $1,492.90