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	$164.85	5.221%	$173.4568	$173.46	$173.45	$173.50
Purchase #2	$174.79	5.394%	$184.2182	$184.22	$184.20	$184.20
Purchase #3	$147.92	3.116%	$152.5292	$152.53	$152.55	$152.50
Purchase #4	$144.30	4.555%	$150.8729	$150.87	$150.85	$150.90
Purchase #5	$130.45	8.612%	$141.6844	$141.68	$141.70	$141.70
Purchase #6	$221.88	9.845%	$243.7241	$243.72	$243.70	$243.70
Purchase #7	$39.60	13.672%	$45.0141	$45.01	$45.00	$45.00
7 purchase totals =	$1,023.79		$1,091.4997	$1,091.49	$1,091.45	$1,091.50