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 $86.34   10.204%   $95.1501   $95.15   $95.15   $95.20  
  Purchase #2 $231.44   5.796%   $244.8543   $244.85   $244.85   $244.90  
  Purchase #3 $57.89   6.794%   $61.823   $61.82   $61.80   $61.80  
  Purchase #4 $115.54   4.153%   $120.3384   $120.34   $120.35   $120.30  
  Purchase #5 $86.93   11.195%   $96.6618   $96.66   $96.65   $96.70  
  Purchase #6 $88.86   9.174%   $97.012   $97.01   $97.00   $97.00  
  Purchase #7 $45.29   9.757%   $49.7089   $49.71   $49.70   $49.70  
  7 purchase totals = $712.29       $765.5485   $765.54   $765.50   $765.60