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 $241.88   10.469%   $267.2024   $267.20   $267.20   $267.20  
  Purchase #2 $195.98   10.418%   $216.3972   $216.40   $216.40   $216.40  
  Purchase #3 $95.77   9.532%   $104.8988   $104.90   $104.90   $104.90  
  Purchase #4 $12.65   5.351%   $13.3269   $13.33   $13.35   $13.30  
  Purchase #5 $161.60   4.593%   $169.0223   $169.02   $169.00   $169.00  
  Purchase #6 $65.35   11.155%   $72.6398   $72.64   $72.65   $72.60  
  Purchase #7 $30.97   5.846%   $32.7805   $32.78   $32.80   $32.80  
  7 purchase totals = $804.20       $876.2679   $876.27   $876.30   $876.20