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	$134.89	8.532%	$146.3988	$146.40	$146.40	$146.40
Purchase #2	$217.31	3.287%	$224.453	$224.45	$224.45	$224.50
Purchase #3	$99.43	7.133%	$106.5223	$106.52	$106.50	$106.50
Purchase #4	$46.96	13.352%	$53.2301	$53.23	$53.25	$53.20
Purchase #5	$30.65	4.662%	$32.0789	$32.08	$32.10	$32.10
Purchase #6	$119.82	12.617%	$134.9377	$134.94	$134.95	$134.90
Purchase #7	$75.28	4.468%	$78.6435	$78.64	$78.65	$78.60
7 purchase totals =	$724.34		$776.2643	$776.26	$776.30	$776.20