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 $41.74   13.366%   $47.319   $47.32   $47.30   $47.30  
  Purchase #2 $108.27   3.154%   $111.6848   $111.68   $111.70   $111.70  
  Purchase #3 $169.49   6.171%   $179.9492   $179.95   $179.95   $179.90  
  Purchase #4 $233.28   5.710%   $246.6003   $246.60   $246.60   $246.60  
  Purchase #5 $112.75   5.504%   $118.9558   $118.96   $118.95   $119.00  
  Purchase #6 $129.43   7.267%   $138.8357   $138.84   $138.85   $138.80  
  Purchase #7 $94.78   6.293%   $100.7445   $100.74   $100.75   $100.70  
  7 purchase totals = $889.74       $944.0893   $944.09   $944.10   $944.00