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	$124.50	13.482%	$141.2851	$141.29	$141.30	$141.30
Purchase #2	$191.53	4.664%	$200.463	$200.46	$200.45	$200.50
Purchase #3	$132.29	6.305%	$140.6309	$140.63	$140.65	$140.60
Purchase #4	$166.26	5.385%	$175.2131	$175.21	$175.20	$175.20
Purchase #5	$187.89	12.337%	$211.07	$211.07	$211.05	$211.10
Purchase #6	$236.27	13.747%	$268.75	$268.75	$268.75	$268.80
Purchase #7	$32.80	8.141%	$35.4702	$35.47	$35.45	$35.50
7 purchase totals =	$1,071.54		$1,172.8823	$1,172.88	$1,172.85	$1,173.00