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 $68.96   9.219%   $75.3174   $75.32   $75.30   $75.30  
  Purchase #2 $143.72   6.631%   $153.2501   $153.25   $153.25   $153.30  
  Purchase #3 $236.42   9.153%   $258.0595   $258.06   $258.05   $258.10  
  Purchase #4 $166.42   13.199%   $188.3858   $188.39   $188.40   $188.40  
  Purchase #5 $94.39   8.384%   $102.3037   $102.30   $102.30   $102.30  
  Purchase #6 $156.48   11.464%   $174.4189   $174.42   $174.40   $174.40  
  Purchase #7 $203.96   5.782%   $215.753   $215.75   $215.75   $215.80  
  7 purchase totals = $1,070.35       $1,167.4884   $1,167.49   $1,167.45   $1,167.60