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 $96.83   5.293%   $101.9552   $101.96   $101.95   $102.00  
  Purchase #2 $24.38   5.539%   $25.7304   $25.73   $25.75   $25.70  
  Purchase #3 $205.78   4.585%   $215.215   $215.22   $215.20   $215.20  
  Purchase #4 $84.73   9.499%   $92.7785   $92.78   $92.80   $92.80  
  Purchase #5 $222.78   12.531%   $250.6966   $250.70   $250.70   $250.70  
  Purchase #6 $194.29   5.408%   $204.7972   $204.80   $204.80   $204.80  
  Purchase #7 $176.93   8.713%   $192.3459   $192.35   $192.35   $192.30  
  7 purchase totals = $1,005.72       $1,083.5188   $1,083.54   $1,083.55   $1,083.50