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 $41.86   10.289%   $46.167   $46.17   $46.15   $46.20  
  Purchase #2 $209.85   4.282%   $218.8358   $218.84   $218.85   $218.80  
  Purchase #3 $145.54   7.437%   $156.3638   $156.36   $156.35   $156.40  
  Purchase #4 $115.26   5.494%   $121.5924   $121.59   $121.60   $121.60  
  Purchase #5 $244.82   9.695%   $268.5553   $268.56   $268.55   $268.60  
  Purchase #6 $45.94   10.343%   $50.6916   $50.69   $50.70   $50.70  
  Purchase #7 $97.32   7.844%   $104.9538   $104.95   $104.95   $105.00  
  7 purchase totals = $900.59       $967.1597   $967.16   $967.15   $967.30