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 $89.56   8.872%   $97.5058   $97.51   $97.50   $97.50  
  Purchase #2 $229.52   13.561%   $260.6452   $260.65   $260.65   $260.60  
  Purchase #3 $236.47   9.164%   $258.1401   $258.14   $258.15   $258.10  
  Purchase #4 $192.35   5.563%   $203.0504   $203.05   $203.05   $203.10  
  Purchase #5 $68.67   9.872%   $75.4491   $75.45   $75.45   $75.40  
  Purchase #6 $216.62   3.466%   $224.128   $224.13   $224.15   $224.10  
  Purchase #7 $53.92   5.783%   $57.0382   $57.04   $57.05   $57.00  
  7 purchase totals = $1,087.11       $1,175.9568   $1,175.97   $1,176.00   $1,175.80