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 $194.57   9.307%   $212.6786   $212.68   $212.70   $212.70  
  Purchase #2 $169.61   10.840%   $187.9957   $188.00   $188.00   $188.00  
  Purchase #3 $224.63   3.351%   $232.1574   $232.16   $232.15   $232.20  
  Purchase #4 $79.27   9.859%   $87.0852   $87.09   $87.10   $87.10  
  Purchase #5 $182.57   4.584%   $190.939   $190.94   $190.95   $190.90  
  Purchase #6 $43.77   11.369%   $48.7462   $48.75   $48.75   $48.70  
  Purchase #7 $96.53   7.698%   $103.9609   $103.96   $103.95   $104.00  
  7 purchase totals = $990.95       $1,063.5630   $1,063.58   $1,063.60   $1,063.60