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 $84.84   11.674%   $94.7442   $94.74   $94.75   $94.70  
  Purchase #2 $206.64   4.820%   $216.6   $216.60   $216.60   $216.60  
  Purchase #3 $133.39   10.653%   $147.6   $147.60   $147.60   $147.60  
  Purchase #4 $180.38   9.105%   $196.8036   $196.80   $196.80   $196.80  
  Purchase #5 $147.96   12.397%   $166.3026   $166.30   $166.30   $166.30  
  Purchase #6 $197.63   12.154%   $221.65   $221.65   $221.65   $221.70  
  Purchase #7 $58.76   13.625%   $66.7661   $66.77   $66.75   $66.80  
  7 purchase totals = $1,009.60       $1,110.4665   $1,110.46   $1,110.45   $1,110.50