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	$172.57	4.426%	$180.2079	$180.21	$180.20	$180.20
Purchase #2	$220.92	10.623%	$244.3883	$244.39	$244.40	$244.40
Purchase #3	$62.83	11.580%	$70.1057	$70.11	$70.10	$70.10
Purchase #4	$70.98	7.511%	$76.3113	$76.31	$76.30	$76.30
Purchase #5	$136.51	11.395%	$152.0653	$152.07	$152.05	$152.10
Purchase #6	$238.92	12.866%	$269.6594	$269.66	$269.65	$269.70
Purchase #7	$105.58	6.389%	$112.3255	$112.33	$112.35	$112.30
7 purchase totals =	$1,008.31		$1,105.0634	$1,105.08	$1,105.05	$1,105.10