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 $132.29   10.328%   $145.9529   $145.95   $145.95   $146.00  
  Purchase #2 $197.96   5.354%   $208.5588   $208.56   $208.55   $208.60  
  Purchase #3 $30.58   8.353%   $33.1343   $33.13   $33.15   $33.10  
  Purchase #4 $211.57   5.548%   $223.3079   $223.31   $223.30   $223.30  
  Purchase #5 $102.53   13.293%   $116.1593   $116.16   $116.15   $116.20  
  Purchase #6 $250.95   7.408%   $269.5404   $269.54   $269.55   $269.50  
  Purchase #7 $243.49   4.295%   $253.9479   $253.95   $253.95   $253.90  
  7 purchase totals = $1,169.37       $1,250.6015   $1,250.60   $1,250.60   $1,250.60