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 $200.74   7.472%   $215.7393   $215.74   $215.75   $215.70  
  Purchase #2 $87.79   8.201%   $94.9897   $94.99   $95.00   $95.00  
  Purchase #3 $187.64   13.778%   $213.493   $213.49   $213.50   $213.50  
  Purchase #4 $212.33   11.224%   $236.1619   $236.16   $236.15   $236.20  
  Purchase #5 $65.29   3.218%   $67.391   $67.39   $67.40   $67.40  
  Purchase #6 $102.69   7.619%   $110.514   $110.51   $110.50   $110.50  
  Purchase #7 $107.46   13.413%   $121.8736   $121.87   $121.85   $121.90  
  7 purchase totals = $963.94       $1,060.1625   $1,060.15   $1,060.15   $1,060.20