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 $214.48   9.440%   $234.7269   $234.73   $234.75   $234.70  
  Purchase #2 $219.77   10.808%   $243.5227   $243.52   $243.50   $243.50  
  Purchase #3 $144.46   11.369%   $160.8837   $160.88   $160.90   $160.90  
  Purchase #4 $202.96   6.660%   $216.4771   $216.48   $216.50   $216.50  
  Purchase #5 $236.80   8.490%   $256.9043   $256.90   $256.90   $256.90  
  Purchase #6 $154.34   4.404%   $161.1371   $161.14   $161.15   $161.10  
  Purchase #7 $200.88   9.681%   $220.3272   $220.33   $220.35   $220.30  
  7 purchase totals = $1,373.69       $1,493.9790   $1,493.98   $1,494.05   $1,493.90