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 $62.75   12.397%   $70.5291   $70.53   $70.55   $70.50  
  Purchase #2 $222.69   13.723%   $253.2497   $253.25   $253.25   $253.20  
  Purchase #3 $213.37   12.825%   $240.7347   $240.73   $240.75   $240.70  
  Purchase #4 $65.72   7.154%   $70.4216   $70.42   $70.40   $70.40  
  Purchase #5 $174.81   11.422%   $194.7768   $194.78   $194.80   $194.80  
  Purchase #6 $185.29   10.822%   $205.3421   $205.34   $205.35   $205.30  
  Purchase #7 $150.84   12.790%   $170.1324   $170.13   $170.15   $170.10  
  7 purchase totals = $1,075.47       $1,205.1864   $1,205.18   $1,205.25   $1,205.00