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 $87.83   8.133%   $94.9732   $94.97   $94.95   $95.00  
  Purchase #2 $85.80   11.475%   $95.6456   $95.65   $95.65   $95.60  
  Purchase #3 $130.80   7.734%   $140.9161   $140.92   $140.90   $140.90  
  Purchase #4 $105.39   10.869%   $116.8448   $116.84   $116.85   $116.80  
  Purchase #5 $216.63   10.168%   $238.6569   $238.66   $238.65   $238.70  
  Purchase #6 $99.89   4.159%   $104.0444   $104.04   $104.05   $104.00  
  Purchase #7 $238.63   3.179%   $246.216   $246.22   $246.20   $246.20  
  7 purchase totals = $964.97       $1,037.2970   $1,037.30   $1,037.25   $1,037.20