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 $87.32   8.407%   $94.661   $94.66   $94.65   $94.70  
  Purchase #2 $44.90   12.580%   $50.5484   $50.55   $50.55   $50.50  
  Purchase #3 $52.95   12.483%   $59.5597   $59.56   $59.55   $59.60  
  Purchase #4 $88.78   13.206%   $100.5043   $100.50   $100.50   $100.50  
  Purchase #5 $141.80   8.385%   $153.6899   $153.69   $153.70   $153.70  
  Purchase #6 $128.35   6.621%   $136.8481   $136.85   $136.85   $136.80  
  Purchase #7 $152.31   3.195%   $157.1763   $157.18   $157.20   $157.20  
  7 purchase totals = $696.41       $752.9877   $752.99   $753.00   $753.00