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 $82.94   13.252%   $93.9312   $93.93   $93.95   $93.90  
  Purchase #2 $132.64   9.781%   $145.6135   $145.61   $145.60   $145.60  
  Purchase #3 $129.68   9.591%   $142.1176   $142.12   $142.10   $142.10  
  Purchase #4 $157.27   11.830%   $175.875   $175.88   $175.90   $175.90  
  Purchase #5 $189.29   4.693%   $198.1734   $198.17   $198.15   $198.20  
  Purchase #6 $140.43   7.686%   $151.2234   $151.22   $151.20   $151.20  
  Purchase #7 $204.77   4.864%   $214.73   $214.73   $214.75   $214.70  
  7 purchase totals = $1,037.02       $1,121.6641   $1,121.66   $1,121.65   $1,121.60