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 $175.41   10.618%   $194.035   $194.04   $194.05   $194.00  
  Purchase #2 $92.30   6.137%   $97.9645   $97.96   $97.95   $98.00  
  Purchase #3 $26.50   5.267%   $27.8958   $27.90   $27.90   $27.90  
  Purchase #4 $159.54   3.655%   $165.3712   $165.37   $165.35   $165.40  
  Purchase #5 $162.88   13.538%   $184.9307   $184.93   $184.95   $184.90  
  Purchase #6 $190.48   13.549%   $216.2881   $216.29   $216.30   $216.30  
  Purchase #7 $174.56   7.114%   $186.9782   $186.98   $187.00   $187.00  
  7 purchase totals = $981.67       $1,073.4635   $1,073.47   $1,073.50   $1,073.50