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 $175.27   9.555%   $192.017   $192.02   $192.00   $192.00  
  Purchase #2 $182.59   12.178%   $204.8258   $204.83   $204.85   $204.80  
  Purchase #3 $65.84   5.515%   $69.4711   $69.47   $69.45   $69.50  
  Purchase #4 $238.57   7.526%   $256.5248   $256.52   $256.50   $256.50  
  Purchase #5 $27.95   3.199%   $28.8441   $28.84   $28.85   $28.80  
  Purchase #6 $140.47   11.574%   $156.728   $156.73   $156.75   $156.70  
  Purchase #7 $31.34   11.375%   $34.9049   $34.90   $34.90   $34.90  
  7 purchase totals = $862.03       $943.3157   $943.31   $943.30   $943.20