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 $60.90   13.643%   $69.2086   $69.21   $69.20   $69.20  
  Purchase #2 $91.96   5.301%   $96.8348   $96.83   $96.85   $96.80  
  Purchase #3 $82.84   5.450%   $87.3548   $87.35   $87.35   $87.40  
  Purchase #4 $162.66   11.208%   $180.8909   $180.89   $180.90   $180.90  
  Purchase #5 $243.80   6.547%   $259.7616   $259.76   $259.75   $259.80  
  Purchase #6 $23.89   6.544%   $25.4534   $25.45   $25.45   $25.50  
  Purchase #7 $7.49   7.370%   $8.042   $8.04   $8.05   $8.00  
  7 purchase totals = $673.54       $727.5461   $727.53   $727.55   $727.60