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 $195.67   3.695%   $202.9   $202.90   $202.90   $202.90  
  Purchase #2 $61.68   11.774%   $68.9422   $68.94   $68.95   $68.90  
  Purchase #3 $33.37   9.297%   $36.4724   $36.47   $36.45   $36.50  
  Purchase #4 $35.68   11.784%   $39.8845   $39.88   $39.90   $39.90  
  Purchase #5 $148.30   8.807%   $161.3608   $161.36   $161.35   $161.40  
  Purchase #6 $183.90   12.607%   $207.0843   $207.08   $207.10   $207.10  
  Purchase #7 $202.93   13.432%   $230.1876   $230.19   $230.20   $230.20  
  7 purchase totals = $861.53       $946.8318   $946.82   $946.85   $946.90