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 $58.70   7.551%   $63.1324   $63.13   $63.15   $63.10  
  Purchase #2 $69.92   6.257%   $74.2949   $74.29   $74.30   $74.30  
  Purchase #3 $13.39   7.435%   $14.3855   $14.39   $14.40   $14.40  
  Purchase #4 $90.53   7.682%   $97.4845   $97.48   $97.50   $97.50  
  Purchase #5 $164.82   7.248%   $176.7662   $176.77   $176.75   $176.80  
  Purchase #6 $21.68   10.567%   $23.9709   $23.97   $23.95   $24.00  
  Purchase #7 $13.79   7.452%   $14.8176   $14.82   $14.80   $14.80  
  7 purchase totals = $432.83       $464.8520   $464.85   $464.85   $464.90