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 $174.51   11.573%   $194.706   $194.71   $194.70   $194.70  
  Purchase #2 $56.31   6.467%   $59.9516   $59.95   $59.95   $60.00  
  Purchase #3 $94.46   4.781%   $98.9761   $98.98   $99.00   $99.00  
  Purchase #4 $129.86   13.461%   $147.3405   $147.34   $147.35   $147.30  
  Purchase #5 $139.74   9.601%   $153.1564   $153.16   $153.15   $153.20  
  Purchase #6 $35.48   4.243%   $36.9854   $36.99   $37.00   $37.00  
  Purchase #7 $67.51   4.573%   $70.5972   $70.60   $70.60   $70.60  
  7 purchase totals = $697.87       $761.7132   $761.73   $761.75   $761.80