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	$104.32	6.735%	$111.346	$111.35	$111.35	$111.30
Purchase #2	$133.90	3.162%	$138.1339	$138.13	$138.15	$138.10
Purchase #3	$103.42	3.762%	$107.3107	$107.31	$107.30	$107.30
Purchase #4	$137.75	6.527%	$146.7409	$146.74	$146.75	$146.70
Purchase #5	$145.78	4.373%	$152.155	$152.16	$152.15	$152.20
Purchase #6	$34.26	3.754%	$35.5461	$35.55	$35.55	$35.50
Purchase #7	$139.98	7.379%	$150.3091	$150.31	$150.30	$150.30
7 purchase totals =	$799.41		$841.5417	$841.55	$841.55	$841.40