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 $88.37   7.578%   $95.0667   $95.07   $95.05   $95.10  
  Purchase #2 $5.49   13.743%   $6.2445   $6.24   $6.25   $6.20  
  Purchase #3 $25.99   11.858%   $29.0719   $29.07   $29.05   $29.10  
  Purchase #4 $59.45   6.196%   $63.1335   $63.13   $63.15   $63.10  
  Purchase #5 $219.39   6.475%   $233.5955   $233.60   $233.60   $233.60  
  Purchase #6 $82.63   4.585%   $86.4186   $86.42   $86.40   $86.40  
  Purchase #7 $220.96   13.212%   $250.1532   $250.15   $250.15   $250.20  
  7 purchase totals = $702.28       $763.6839   $763.68   $763.65   $763.70