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 $167.87   11.364%   $186.9467   $186.95   $186.95   $186.90  
  Purchase #2 $227.96   5.164%   $239.7319   $239.73   $239.75   $239.70  
  Purchase #3 $161.71   6.437%   $172.1193   $172.12   $172.10   $172.10  
  Purchase #4 $169.53   5.171%   $178.2964   $178.30   $178.30   $178.30  
  Purchase #5 $79.37   6.297%   $84.3679   $84.37   $84.35   $84.40  
  Purchase #6 $95.86   5.575%   $101.2042   $101.20   $101.20   $101.20  
  Purchase #7 $68.74   5.839%   $72.7537   $72.75   $72.75   $72.80  
  7 purchase totals = $971.04       $1,035.4201   $1,035.42   $1,035.40   $1,035.40