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 $194.68   7.870%   $210.0013   $210.00   $210.00   $210.00  
  Purchase #2 $86.87   9.302%   $94.9506   $94.95   $94.95   $95.00  
  Purchase #3 $120.43   8.390%   $130.5341   $130.53   $130.55   $130.50  
  Purchase #4 $14.60   11.442%   $16.2705   $16.27   $16.25   $16.30  
  Purchase #5 $84.29   4.819%   $88.3519   $88.35   $88.35   $88.40  
  Purchase #6 $117.46   7.735%   $126.5455   $126.55   $126.55   $126.50  
  Purchase #7 $101.78   7.361%   $109.272   $109.27   $109.25   $109.30  
  7 purchase totals = $720.11       $775.9259   $775.92   $775.90   $776.00