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 $193.68   5.425%   $204.1871   $204.19   $204.20   $204.20  
  Purchase #2 $82.91   4.155%   $86.3549   $86.35   $86.35   $86.40  
  Purchase #3 $88.27   3.777%   $91.604   $91.60   $91.60   $91.60  
  Purchase #4 $247.60   12.756%   $279.1839   $279.18   $279.20   $279.20  
  Purchase #5 $73.64   12.251%   $82.6616   $82.66   $82.65   $82.70  
  Purchase #6 $45.34   13.665%   $51.5357   $51.54   $51.55   $51.50  
  Purchase #7 $224.72   5.511%   $237.1043   $237.10   $237.10   $237.10  
  7 purchase totals = $956.16       $1,032.6315   $1,032.62   $1,032.65   $1,032.70