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 $210.77   10.527%   $232.9578   $232.96   $232.95   $233.00  
  Purchase #2 $126.47   4.358%   $131.9816   $131.98   $132.00   $132.00  
  Purchase #3 $12.63   12.425%   $14.1993   $14.20   $14.20   $14.20  
  Purchase #4 $176.64   10.578%   $195.325   $195.33   $195.35   $195.30  
  Purchase #5 $193.65   11.566%   $216.0476   $216.05   $216.05   $216.00  
  Purchase #6 $26.60   9.629%   $29.1613   $29.16   $29.15   $29.20  
  Purchase #7 $202.89   10.603%   $224.4024   $224.40   $224.40   $224.40  
  7 purchase totals = $949.65       $1,044.0750   $1,044.08   $1,044.10   $1,044.10