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	$152.66	12.345%	$171.5059	$171.51	$171.50	$171.50
Purchase #2	$86.71	6.222%	$92.1051	$92.11	$92.10	$92.10
Purchase #3	$248.77	7.216%	$266.7212	$266.72	$266.70	$266.70
Purchase #4	$237.34	4.210%	$247.332	$247.33	$247.35	$247.30
Purchase #5	$140.76	4.259%	$146.755	$146.76	$146.75	$146.80
Purchase #6	$185.67	6.728%	$198.1619	$198.16	$198.15	$198.20
Purchase #7	$18.40	4.746%	$19.2733	$19.27	$19.25	$19.30
7 purchase totals =	$1,070.31		$1,141.8544	$1,141.86	$1,141.80	$1,141.90