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 $51.65   3.483%   $53.449   $53.45   $53.45   $53.40  
  Purchase #2 $207.30   11.785%   $231.7303   $231.73   $231.75   $231.70  
  Purchase #3 $106.54   5.700%   $112.6128   $112.61   $112.60   $112.60  
  Purchase #4 $148.29   6.575%   $158.0401   $158.04   $158.05   $158.00  
  Purchase #5 $80.46   4.658%   $84.2078   $84.21   $84.20   $84.20  
  Purchase #6 $118.53   6.794%   $126.5829   $126.58   $126.60   $126.60  
  Purchase #7 $96.33   5.684%   $101.8054   $101.81   $101.80   $101.80  
  7 purchase totals = $809.10       $868.4283   $868.43   $868.45   $868.30