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 $57.45   8.521%   $62.3453   $62.35   $62.35   $62.30  
  Purchase #2 $139.47   10.227%   $153.7336   $153.73   $153.75   $153.70  
  Purchase #3 $91.46   11.483%   $101.9624   $101.96   $101.95   $102.00  
  Purchase #4 $108.79   5.530%   $114.8061   $114.81   $114.80   $114.80  
  Purchase #5 $130.35   4.234%   $135.869   $135.87   $135.85   $135.90  
  Purchase #6 $65.30   9.483%   $71.4924   $71.49   $71.50   $71.50  
  Purchase #7 $113.53   5.495%   $119.7685   $119.77   $119.75   $119.80  
  7 purchase totals = $706.35       $759.9773   $759.98   $759.95   $760.00