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 $211.27   11.125%   $234.7738   $234.77   $234.75   $234.80  
  Purchase #2 $200.70   4.520%   $209.7716   $209.77   $209.75   $209.80  
  Purchase #3 $202.45   7.203%   $217.0325   $217.03   $217.05   $217.00  
  Purchase #4 $54.30   6.151%   $57.64   $57.64   $57.65   $57.60  
  Purchase #5 $7.54   11.164%   $8.3818   $8.38   $8.40   $8.40  
  Purchase #6 $194.46   5.613%   $205.375   $205.38   $205.40   $205.40  
  Purchase #7 $150.42   7.735%   $162.055   $162.06   $162.05   $162.10  
  7 purchase totals = $1,021.14       $1,095.0297   $1,095.03   $1,095.05   $1,095.10