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	$58.89	3.232%	$60.7933	$60.79	$60.80	$60.80
Purchase #2	$116.76	3.422%	$120.7555	$120.76	$120.75	$120.80
Purchase #3	$81.90	7.596%	$88.1211	$88.12	$88.10	$88.10
Purchase #4	$214.39	4.407%	$223.8382	$223.84	$223.85	$223.80
Purchase #5	$197.65	5.455%	$208.4318	$208.43	$208.45	$208.40
Purchase #6	$155.90	10.821%	$172.7699	$172.77	$172.75	$172.80
Purchase #7	$196.78	13.597%	$223.5362	$223.54	$223.55	$223.50
7 purchase totals =	$1,022.27		$1,098.2460	$1,098.25	$1,098.25	$1,098.20