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 $43.88   11.558%   $48.9517   $48.95   $48.95   $49.00  
  Purchase #2 $169.68   8.761%   $184.5457   $184.55   $184.55   $184.50  
  Purchase #3 $85.53   13.637%   $97.1937   $97.19   $97.20   $97.20  
  Purchase #4 $42.56   9.184%   $46.4687   $46.47   $46.45   $46.50  
  Purchase #5 $54.63   12.279%   $61.338   $61.34   $61.35   $61.30  
  Purchase #6 $100.67   7.107%   $107.8246   $107.82   $107.80   $107.80  
  Purchase #7 $16.44   8.852%   $17.8953   $17.90   $17.90   $17.90  
  7 purchase totals = $513.39       $564.2177   $564.22   $564.20   $564.20