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 $114.70   11.563%   $127.9628   $127.96   $127.95   $128.00  
  Purchase #2 $217.81   9.562%   $238.637   $238.64   $238.65   $238.60  
  Purchase #3 $74.68   13.283%   $84.5997   $84.60   $84.60   $84.60  
  Purchase #4 $118.89   6.244%   $126.3135   $126.31   $126.30   $126.30  
  Purchase #5 $209.71   4.268%   $218.6604   $218.66   $218.65   $218.70  
  Purchase #6 $40.97   5.421%   $43.191   $43.19   $43.20   $43.20  
  Purchase #7 $177.73   10.846%   $197.0066   $197.01   $197.00   $197.00  
  7 purchase totals = $954.49       $1,036.3710   $1,036.37   $1,036.35   $1,036.40