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 $71.35   3.201%   $73.6339   $73.63   $73.65   $73.60  
  Purchase #2 $184.88   10.690%   $204.6437   $204.64   $204.65   $204.60  
  Purchase #3 $158.84   10.856%   $176.0837   $176.08   $176.10   $176.10  
  Purchase #4 $243.90   13.199%   $276.0924   $276.09   $276.10   $276.10  
  Purchase #5 $200.56   7.432%   $215.4656   $215.47   $215.45   $215.50  
  Purchase #6 $90.98   5.379%   $95.8738   $95.87   $95.85   $95.90  
  Purchase #7 $126.97   4.215%   $132.3218   $132.32   $132.30   $132.30  
  7 purchase totals = $1,077.48       $1,174.1149   $1,174.10   $1,174.10   $1,174.10