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 $32.82   10.751%   $36.3485   $36.35   $36.35   $36.30  
  Purchase #2 $120.54   8.415%   $130.6834   $130.68   $130.70   $130.70  
  Purchase #3 $176.94   10.276%   $195.1224   $195.12   $195.10   $195.10  
  Purchase #4 $154.78   8.735%   $168.3   $168.30   $168.30   $168.30  
  Purchase #5 $201.82   10.587%   $223.1867   $223.19   $223.20   $223.20  
  Purchase #6 $198.63   10.541%   $219.5676   $219.57   $219.55   $219.60  
  Purchase #7 $234.70   4.556%   $245.3929   $245.39   $245.40   $245.40  
  7 purchase totals = $1,120.23       $1,218.6015   $1,218.60   $1,218.60   $1,218.60