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 $221.89   3.308%   $229.2301   $229.23   $229.25   $229.20  
  Purchase #2 $85.31   11.564%   $95.1752   $95.18   $95.20   $95.20  
  Purchase #3 $104.37   11.816%   $116.7024   $116.70   $116.70   $116.70  
  Purchase #4 $229.63   7.428%   $246.6869   $246.69   $246.70   $246.70  
  Purchase #5 $33.66   12.502%   $37.8682   $37.87   $37.85   $37.90  
  Purchase #6 $226.33   10.790%   $250.751   $250.75   $250.75   $250.80  
  Purchase #7 $80.82   7.672%   $87.0205   $87.02   $87.00   $87.00  
  7 purchase totals = $982.01       $1,063.4343   $1,063.44   $1,063.45   $1,063.50