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 $161.51   8.469%   $175.1883   $175.19   $175.20   $175.20  
  Purchase #2 $192.42   11.205%   $213.9807   $213.98   $214.00   $214.00  
  Purchase #3 $159.56   6.616%   $170.1165   $170.12   $170.10   $170.10  
  Purchase #4 $85.86   11.817%   $96.0061   $96.01   $96.00   $96.00  
  Purchase #5 $105.28   13.448%   $119.4381   $119.44   $119.45   $119.40  
  Purchase #6 $36.31   9.866%   $39.8923   $39.89   $39.90   $39.90  
  Purchase #7 $102.33   8.201%   $110.7221   $110.72   $110.70   $110.70  
  7 purchase totals = $843.27       $925.3441   $925.35   $925.35   $925.30