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 $82.45   13.630%   $93.6879   $93.69   $93.70   $93.70  
  Purchase #2 $206.60   5.734%   $218.4464   $218.45   $218.45   $218.40  
  Purchase #3 $107.85   12.496%   $121.3269   $121.33   $121.35   $121.30  
  Purchase #4 $153.51   6.116%   $162.8987   $162.90   $162.90   $162.90  
  Purchase #5 $233.77   5.322%   $246.2112   $246.21   $246.20   $246.20  
  Purchase #6 $187.41   11.521%   $209.0015   $209.00   $209.00   $209.00  
  Purchase #7 $147.52   10.740%   $163.3636   $163.36   $163.35   $163.40  
  7 purchase totals = $1,119.11       $1,214.9362   $1,214.94   $1,214.95   $1,214.90