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 $101.62   10.547%   $112.3379   $112.34   $112.35   $112.30  
  Purchase #2 $45.39   3.627%   $47.0363   $47.04   $47.05   $47.00  
  Purchase #3 $196.63   4.282%   $205.0497   $205.05   $205.05   $205.00  
  Purchase #4 $204.64   13.703%   $232.6818   $232.68   $232.70   $232.70  
  Purchase #5 $28.87   13.772%   $32.846   $32.85   $32.85   $32.80  
  Purchase #6 $225.62   7.168%   $241.7924   $241.79   $241.80   $241.80  
  Purchase #7 $64.78   9.793%   $71.1239   $71.12   $71.10   $71.10  
  7 purchase totals = $867.55       $942.8680   $942.87   $942.90   $942.70