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 $182.94   6.294%   $194.4542   $194.45   $194.45   $194.50  
  Purchase #2 $96.69   11.646%   $107.9505   $107.95   $107.95   $108.00  
  Purchase #3 $193.95   10.266%   $213.8609   $213.86   $213.85   $213.90  
  Purchase #4 $99.97   6.567%   $106.535   $106.54   $106.55   $106.50  
  Purchase #5 $47.99   6.204%   $50.9673   $50.97   $50.95   $51.00  
  Purchase #6 $218.95   10.401%   $241.723   $241.72   $241.70   $241.70  
  Purchase #7 $24.56   4.204%   $25.5925   $25.59   $25.60   $25.60  
  7 purchase totals = $865.05       $941.0834   $941.08   $941.05   $941.20