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	$50.27	5.789%	$53.1801	$53.18	$53.20	$53.20
Purchase #2	$31.45	5.727%	$33.2511	$33.25	$33.25	$33.30
Purchase #3	$70.80	4.764%	$74.1729	$74.17	$74.15	$74.20
Purchase #4	$212.71	4.731%	$222.7733	$222.77	$222.75	$222.80
Purchase #5	$146.43	6.769%	$156.3418	$156.34	$156.35	$156.30
Purchase #6	$100.83	5.300%	$106.174	$106.17	$106.15	$106.20
Purchase #7	$76.62	9.183%	$83.656	$83.66	$83.65	$83.70
7 purchase totals =	$689.11		$729.5492	$729.54	$729.50	$729.70