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 $232.73   4.692%   $243.6497   $243.65   $243.65   $243.60  
  Purchase #2 $91.94   6.551%   $97.963   $97.96   $97.95   $98.00  
  Purchase #3 $154.62   10.726%   $171.2045   $171.20   $171.20   $171.20  
  Purchase #4 $81.68   5.453%   $86.134   $86.13   $86.15   $86.10  
  Purchase #5 $239.60   6.219%   $254.5007   $254.50   $254.50   $254.50  
  Purchase #6 $136.80   5.231%   $143.956   $143.96   $143.95   $144.00  
  Purchase #7 $89.70   5.120%   $94.2926   $94.29   $94.30   $94.30  
  7 purchase totals = $1,027.07       $1,091.7005   $1,091.69   $1,091.70   $1,091.70