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 $63.37   8.259%   $68.6037   $68.60   $68.60   $68.60  
  Purchase #2 $88.36   10.862%   $97.9577   $97.96   $97.95   $98.00  
  Purchase #3 $141.43   3.125%   $145.8497   $145.85   $145.85   $145.80  
  Purchase #4 $108.99   8.262%   $117.9948   $117.99   $118.00   $118.00  
  Purchase #5 $215.85   5.711%   $228.1772   $228.18   $228.20   $228.20  
  Purchase #6 $237.52   12.835%   $268.0057   $268.01   $268.00   $268.00  
  Purchase #7 $102.57   8.168%   $110.9479   $110.95   $110.95   $110.90  
  7 purchase totals = $958.09       $1,037.5367   $1,037.54   $1,037.55   $1,037.50