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 $244.96   6.212%   $260.1769   $260.18   $260.20   $260.20  
  Purchase #2 $90.38   8.706%   $98.2485   $98.25   $98.25   $98.20  
  Purchase #3 $169.27   11.580%   $188.8715   $188.87   $188.85   $188.90  
  Purchase #4 $32.28   7.186%   $34.5996   $34.60   $34.60   $34.60  
  Purchase #5 $212.52   6.174%   $225.641   $225.64   $225.65   $225.60  
  Purchase #6 $243.57   11.418%   $271.3808   $271.38   $271.40   $271.40  
  Purchase #7 $19.53   13.544%   $22.1751   $22.18   $22.20   $22.20  
  7 purchase totals = $1,012.51       $1,101.0934   $1,101.10   $1,101.15   $1,101.10