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 $48.99   10.119%   $53.9473   $53.95   $53.95   $53.90  
  Purchase #2 $222.56   6.605%   $237.2601   $237.26   $237.25   $237.30  
  Purchase #3 $167.84   6.413%   $178.6036   $178.60   $178.60   $178.60  
  Purchase #4 $118.41   4.786%   $124.0771   $124.08   $124.10   $124.10  
  Purchase #5 $10.36   5.743%   $10.955   $10.96   $10.95   $11.00  
  Purchase #6 $149.70   4.457%   $156.3721   $156.37   $156.35   $156.40  
  Purchase #7 $103.67   8.769%   $112.7608   $112.76   $112.75   $112.80  
  7 purchase totals = $821.53       $873.9760   $873.98   $873.95   $874.10