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 $173.50   12.766%   $195.649   $195.65   $195.65   $195.60  
  Purchase #2 $193.35   12.575%   $217.6638   $217.66   $217.65   $217.70  
  Purchase #3 $32.63   13.746%   $37.1153   $37.12   $37.10   $37.10  
  Purchase #4 $183.32   5.386%   $193.1936   $193.19   $193.20   $193.20  
  Purchase #5 $234.27   10.701%   $259.3392   $259.34   $259.35   $259.30  
  Purchase #6 $32.37   12.815%   $36.5182   $36.52   $36.50   $36.50  
  Purchase #7 $67.73   11.516%   $75.5298   $75.53   $75.55   $75.50  
  7 purchase totals = $917.17       $1,015.0089   $1,015.01   $1,015.00   $1,014.90