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 $213.65   13.814%   $243.1636   $243.16   $243.15   $243.20  
  Purchase #2 $162.61   9.835%   $178.6027   $178.60   $178.60   $178.60  
  Purchase #3 $232.28   10.221%   $256.0213   $256.02   $256.00   $256.00  
  Purchase #4 $88.70   12.182%   $99.5054   $99.51   $99.50   $99.50  
  Purchase #5 $123.43   4.727%   $129.2645   $129.26   $129.25   $129.30  
  Purchase #6 $235.30   13.638%   $267.3902   $267.39   $267.40   $267.40  
  Purchase #7 $18.27   13.804%   $20.792   $20.79   $20.80   $20.80  
  7 purchase totals = $1,074.24       $1,194.7397   $1,194.73   $1,194.70   $1,194.80