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	$135.46	8.328%	$146.7411	$146.74	$146.75	$146.70
Purchase #2	$50.58	13.524%	$57.4204	$57.42	$57.40	$57.40
Purchase #3	$35.28	7.154%	$37.8039	$37.80	$37.80	$37.80
Purchase #4	$74.79	5.191%	$78.6723	$78.67	$78.65	$78.70
Purchase #5	$135.46	11.647%	$151.237	$151.24	$151.25	$151.20
Purchase #6	$46.89	13.316%	$53.1339	$53.13	$53.15	$53.10
Purchase #7	$197.28	11.226%	$219.4267	$219.43	$219.45	$219.40
7 purchase totals =	$675.74		$744.4353	$744.43	$744.45	$744.30