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 $85.96   11.347%   $95.7139   $95.71   $95.70   $95.70  
  Purchase #2 $248.51   4.731%   $260.267   $260.27   $260.25   $260.30  
  Purchase #3 $210.75   6.770%   $225.0178   $225.02   $225.00   $225.00  
  Purchase #4 $194.59   7.435%   $209.0578   $209.06   $209.05   $209.10  
  Purchase #5 $62.63   9.385%   $68.5078   $68.51   $68.50   $68.50  
  Purchase #6 $238.40   6.478%   $253.8436   $253.84   $253.85   $253.80  
  Purchase #7 $177.63   6.572%   $189.3038   $189.30   $189.30   $189.30  
  7 purchase totals = $1,218.47       $1,301.7117   $1,301.71   $1,301.65   $1,301.70