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 $53.65   9.422%   $58.7049   $58.70   $58.70   $58.70  
  Purchase #2 $65.34   11.259%   $72.6966   $72.70   $72.70   $72.70  
  Purchase #3 $80.25   5.413%   $84.5939   $84.59   $84.60   $84.60  
  Purchase #4 $231.28   5.833%   $244.7706   $244.77   $244.75   $244.80  
  Purchase #5 $204.95   3.772%   $212.6807   $212.68   $212.70   $212.70  
  Purchase #6 $64.28   7.654%   $69.2   $69.20   $69.20   $69.20  
  Purchase #7 $12.26   10.789%   $13.5827   $13.58   $13.60   $13.60  
  7 purchase totals = $712.01       $756.2294   $756.22   $756.25   $756.30