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	$84.64	8.346%	$91.7041	$91.70	$91.70	$91.70
Purchase #2	$62.79	4.245%	$65.4554	$65.46	$65.45	$65.50
Purchase #3	$98.45	6.309%	$104.6612	$104.66	$104.65	$104.70
Purchase #4	$237.34	6.859%	$253.6192	$253.62	$253.60	$253.60
Purchase #5	$33.51	11.139%	$37.2427	$37.24	$37.25	$37.20
Purchase #6	$127.89	12.839%	$144.3098	$144.31	$144.30	$144.30
Purchase #7	$80.90	10.528%	$89.4172	$89.42	$89.40	$89.40
7 purchase totals =	$725.52		$786.4096	$786.41	$786.35	$786.40