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	$74.39	12.170%	$83.4433	$83.44	$83.45	$83.40
Purchase #2	$152.89	3.364%	$158.0332	$158.03	$158.05	$158.00
Purchase #3	$126.68	11.399%	$141.1203	$141.12	$141.10	$141.10
Purchase #4	$190.29	4.209%	$198.2993	$198.30	$198.30	$198.30
Purchase #5	$211.72	5.577%	$223.5276	$223.53	$223.55	$223.50
Purchase #6	$196.87	7.218%	$211.0801	$211.08	$211.10	$211.10
Purchase #7	$53.63	3.762%	$55.6476	$55.65	$55.65	$55.60
7 purchase totals =	$1,006.47		$1,071.1514	$1,071.15	$1,071.20	$1,071.00