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 $82.33   12.425%   $92.5595   $92.56   $92.55   $92.60  
  Purchase #2 $209.67   7.361%   $225.1038   $225.10   $225.10   $225.10  
  Purchase #3 $244.87   7.844%   $264.0776   $264.08   $264.10   $264.10  
  Purchase #4 $187.63   4.244%   $195.593   $195.59   $195.60   $195.60  
  Purchase #5 $101.98   3.847%   $105.9032   $105.90   $105.90   $105.90  
  Purchase #6 $96.47   10.284%   $106.391   $106.39   $106.40   $106.40  
  Purchase #7 $207.28   3.158%   $213.8259   $213.83   $213.85   $213.80  
  7 purchase totals = $1,130.23       $1,203.4540   $1,203.45   $1,203.50   $1,203.50