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 $195.71   10.121%   $215.5178   $215.52   $215.50   $215.50  
  Purchase #2 $189.44   11.205%   $210.6668   $210.67   $210.65   $210.70  
  Purchase #3 $60.88   10.730%   $67.4124   $67.41   $67.40   $67.40  
  Purchase #4 $44.85   3.333%   $46.3449   $46.34   $46.35   $46.30  
  Purchase #5 $105.67   13.851%   $120.3064   $120.31   $120.30   $120.30  
  Purchase #6 $101.66   11.399%   $113.2482   $113.25   $113.25   $113.20  
  Purchase #7 $182.87   13.804%   $208.1134   $208.11   $208.10   $208.10  
  7 purchase totals = $881.08       $981.6099   $981.61   $981.55   $981.50