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 $167.86   8.849%   $182.7139   $182.71   $182.70   $182.70  
  Purchase #2 $178.95   9.152%   $195.3275   $195.33   $195.35   $195.30  
  Purchase #3 $29.37   7.244%   $31.4976   $31.50   $31.50   $31.50  
  Purchase #4 $32.96   5.356%   $34.7253   $34.73   $34.75   $34.70  
  Purchase #5 $236.52   6.339%   $251.513   $251.51   $251.50   $251.50  
  Purchase #6 $179.55   6.495%   $191.2118   $191.21   $191.20   $191.20  
  Purchase #7 $196.90   10.782%   $218.1298   $218.13   $218.15   $218.10  
  7 purchase totals = $1,022.11       $1,105.1189   $1,105.12   $1,105.15   $1,105.00