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 $59.75   7.114%   $64.0006   $64.00   $64.00   $64.00  
  Purchase #2 $185.90   8.316%   $201.3594   $201.36   $201.35   $201.40  
  Purchase #3 $249.68   6.339%   $265.5072   $265.51   $265.50   $265.50  
  Purchase #4 $95.81   9.586%   $104.9943   $104.99   $105.00   $105.00  
  Purchase #5 $93.90   11.356%   $104.5633   $104.56   $104.55   $104.60  
  Purchase #6 $189.34   6.603%   $201.8421   $201.84   $201.85   $201.80  
  Purchase #7 $173.96   10.548%   $192.3093   $192.31   $192.30   $192.30  
  7 purchase totals = $1,048.34       $1,134.5762   $1,134.57   $1,134.55   $1,134.60