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 $84.91   11.618%   $94.7748   $94.77   $94.75   $94.80  
  Purchase #2 $212.63   6.454%   $226.3531   $226.35   $226.35   $226.40  
  Purchase #3 $206.37   4.646%   $215.958   $215.96   $215.95   $216.00  
  Purchase #4 $236.82   7.257%   $254.006   $254.01   $254.00   $254.00  
  Purchase #5 $34.70   6.247%   $36.8677   $36.87   $36.85   $36.90  
  Purchase #6 $116.60   13.852%   $132.7514   $132.75   $132.75   $132.80  
  Purchase #7 $77.26   11.429%   $86.09   $86.09   $86.10   $86.10  
  7 purchase totals = $969.29       $1,046.8010   $1,046.80   $1,046.75   $1,047.00