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 $119.77   10.511%   $132.359   $132.36   $132.35   $132.40  
  Purchase #2 $92.74   3.132%   $95.6446   $95.64   $95.65   $95.60  
  Purchase #3 $111.92   4.640%   $117.1131   $117.11   $117.10   $117.10  
  Purchase #4 $111.97   13.267%   $126.8251   $126.83   $126.85   $126.80  
  Purchase #5 $243.49   4.403%   $254.2109   $254.21   $254.20   $254.20  
  Purchase #6 $211.50   10.521%   $233.7519   $233.75   $233.75   $233.80  
  Purchase #7 $154.66   6.461%   $164.6526   $164.65   $164.65   $164.70  
  7 purchase totals = $1,046.05       $1,124.5572   $1,124.55   $1,124.55   $1,124.60