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 $185.52   4.731%   $194.297   $194.30   $194.30   $194.30  
  Purchase #2 $222.63   5.382%   $234.6119   $234.61   $234.60   $234.60  
  Purchase #3 $212.52   5.219%   $223.6114   $223.61   $223.60   $223.60  
  Purchase #4 $236.78   4.268%   $246.8858   $246.89   $246.90   $246.90  
  Purchase #5 $144.61   4.229%   $150.7256   $150.73   $150.75   $150.70  
  Purchase #6 $156.31   4.477%   $163.308   $163.31   $163.30   $163.30  
  Purchase #7 $84.75   3.750%   $87.9281   $87.93   $87.95   $87.90  
  7 purchase totals = $1,243.12       $1,301.3678   $1,301.38   $1,301.40   $1,301.30