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 $29.69   11.287%   $33.0411   $33.04   $33.05   $33.00  
  Purchase #2 $92.75   10.206%   $102.2161   $102.22   $102.20   $102.20  
  Purchase #3 $31.57   5.474%   $33.2981   $33.30   $33.30   $33.30  
  Purchase #4 $67.82   5.581%   $71.605   $71.61   $71.60   $71.60  
  Purchase #5 $193.64   4.323%   $202.0111   $202.01   $202.00   $202.00  
  Purchase #6 $74.90   10.132%   $82.4889   $82.49   $82.50   $82.50  
  Purchase #7 $195.96   4.442%   $204.6645   $204.66   $204.65   $204.70  
  7 purchase totals = $686.33       $729.3248   $729.33   $729.30   $729.30