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 $42.95   3.829%   $44.5946   $44.59   $44.60   $44.60  
  Purchase #2 $67.79   4.643%   $70.9375   $70.94   $70.95   $70.90  
  Purchase #3 $94.70   4.846%   $99.2892   $99.29   $99.30   $99.30  
  Purchase #4 $158.52   5.616%   $167.4225   $167.42   $167.40   $167.40  
  Purchase #5 $143.73   7.436%   $154.4178   $154.42   $154.40   $154.40  
  Purchase #6 $212.68   13.606%   $241.6172   $241.62   $241.60   $241.60  
  Purchase #7 $11.88   7.810%   $12.8078   $12.81   $12.80   $12.80  
  7 purchase totals = $732.25       $791.0866   $791.09   $791.05   $791.00