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	$155.37	3.454%	$160.7365	$160.74	$160.75	$160.70
Purchase #2	$165.30	4.565%	$172.8459	$172.85	$172.85	$172.80
Purchase #3	$159.37	12.811%	$179.7869	$179.79	$179.80	$179.80
Purchase #4	$229.33	5.625%	$242.2298	$242.23	$242.25	$242.20
Purchase #5	$77.59	6.735%	$82.8157	$82.82	$82.80	$82.80
Purchase #6	$223.70	10.482%	$247.1482	$247.15	$247.15	$247.10
Purchase #7	$112.63	13.507%	$127.8429	$127.84	$127.85	$127.80
7 purchase totals =	$1,123.29		$1,213.4059	$1,213.42	$1,213.45	$1,213.20