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 $218.76   6.853%   $233.7516   $233.75   $233.75   $233.80  
  Purchase #2 $45.57   3.147%   $47.0041   $47.00   $47.00   $47.00  
  Purchase #3 $91.29   3.211%   $94.2213   $94.22   $94.20   $94.20  
  Purchase #4 $147.30   13.450%   $167.1119   $167.11   $167.10   $167.10  
  Purchase #5 $168.67   6.162%   $179.0634   $179.06   $179.05   $179.10  
  Purchase #6 $247.51   6.245%   $262.967   $262.97   $262.95   $263.00  
  Purchase #7 $213.63   3.804%   $221.7565   $221.76   $221.75   $221.80  
  7 purchase totals = $1,132.73       $1,205.8758   $1,205.87   $1,205.80   $1,206.00