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 $43.85   5.183%   $46.1227   $46.12   $46.10   $46.10  
  Purchase #2 $195.99   6.200%   $208.1414   $208.14   $208.15   $208.10  
  Purchase #3 $190.47   10.686%   $210.8236   $210.82   $210.80   $210.80  
  Purchase #4 $133.27   12.258%   $149.6062   $149.61   $149.60   $149.60  
  Purchase #5 $112.78   6.660%   $120.2911   $120.29   $120.30   $120.30  
  Purchase #6 $44.83   6.341%   $47.6727   $47.67   $47.65   $47.70  
  Purchase #7 $247.90   9.647%   $271.8149   $271.81   $271.80   $271.80  
  7 purchase totals = $969.09       $1,054.4726   $1,054.46   $1,054.40   $1,054.40