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 $86.36   7.657%   $92.9726   $92.97   $92.95   $93.00  
  Purchase #2 $138.62   9.633%   $151.9733   $151.97   $151.95   $152.00  
  Purchase #3 $87.67   5.239%   $92.263   $92.26   $92.25   $92.30  
  Purchase #4 $247.61   9.234%   $270.4743   $270.47   $270.45   $270.50  
  Purchase #5 $181.63   3.773%   $188.4829   $188.48   $188.50   $188.50  
  Purchase #6 $168.25   3.111%   $173.4843   $173.48   $173.50   $173.50  
  Purchase #7 $101.91   5.731%   $107.7505   $107.75   $107.75   $107.80  
  7 purchase totals = $1,012.05       $1,077.4009   $1,077.38   $1,077.35   $1,077.60