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 $43.92   6.447%   $46.7515   $46.75   $46.75   $46.80  
  Purchase #2 $190.69   7.530%   $205.049   $205.05   $205.05   $205.00  
  Purchase #3 $86.43   10.230%   $95.2718   $95.27   $95.25   $95.30  
  Purchase #4 $70.72   6.133%   $75.0573   $75.06   $75.05   $75.10  
  Purchase #5 $148.64   3.514%   $153.8632   $153.86   $153.85   $153.90  
  Purchase #6 $99.98   5.150%   $105.129   $105.13   $105.15   $105.10  
  Purchase #7 $20.69   9.712%   $22.6994   $22.70   $22.70   $22.70  
  7 purchase totals = $661.07       $703.8212   $703.82   $703.80   $703.90