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	$13.83	8.800%	$15.047	$15.05	$15.05	$15.00
Purchase #2	$67.33	9.519%	$73.7391	$73.74	$73.75	$73.70
Purchase #3	$183.26	4.231%	$191.0137	$191.01	$191.00	$191.00
Purchase #4	$103.74	8.309%	$112.3598	$112.36	$112.35	$112.40
Purchase #5	$81.78	4.529%	$85.4838	$85.48	$85.50	$85.50
Purchase #6	$9.89	4.629%	$10.3478	$10.35	$10.35	$10.30
Purchase #7	$157.43	11.485%	$175.5108	$175.51	$175.50	$175.50
7 purchase totals =	$617.26		$663.5020	$663.50	$663.50	$663.40