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 $69.43   8.460%   $75.3038   $75.30   $75.30   $75.30  
  Purchase #2 $214.67   4.670%   $224.6951   $224.70   $224.70   $224.70  
  Purchase #3 $60.83   13.862%   $69.2623   $69.26   $69.25   $69.30  
  Purchase #4 $244.74   8.273%   $264.9873   $264.99   $265.00   $265.00  
  Purchase #5 $186.85   10.440%   $206.3571   $206.36   $206.35   $206.40  
  Purchase #6 $123.65   11.375%   $137.7152   $137.72   $137.70   $137.70  
  Purchase #7 $166.70   4.865%   $174.81   $174.81   $174.80   $174.80  
  7 purchase totals = $1,066.87       $1,153.1308   $1,153.14   $1,153.10   $1,153.20