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 $184.46   5.151%   $193.9615   $193.96   $193.95   $194.00  
  Purchase #2 $52.87   11.369%   $58.8808   $58.88   $58.90   $58.90  
  Purchase #3 $31.50   4.257%   $32.841   $32.84   $32.85   $32.80  
  Purchase #4 $49.67   9.683%   $54.4795   $54.48   $54.50   $54.50  
  Purchase #5 $103.40   13.558%   $117.419   $117.42   $117.40   $117.40  
  Purchase #6 $115.71   7.575%   $124.475   $124.48   $124.50   $124.50  
  Purchase #7 $100.62   12.302%   $112.9983   $113.00   $113.00   $113.00  
  7 purchase totals = $638.23       $695.0551   $695.06   $695.10   $695.10