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	$155.50	7.481%	$167.133	$167.13	$167.15	$167.10
Purchase #2	$247.30	5.243%	$260.2659	$260.27	$260.25	$260.30
Purchase #3	$148.60	5.386%	$156.6036	$156.60	$156.60	$156.60
Purchase #4	$131.40	6.326%	$139.7124	$139.71	$139.70	$139.70
Purchase #5	$230.49	6.111%	$244.5752	$244.58	$244.60	$244.60
Purchase #6	$33.37	4.809%	$34.9748	$34.97	$34.95	$35.00
Purchase #7	$200.62	9.123%	$218.9226	$218.92	$218.90	$218.90
7 purchase totals =	$1,147.28		$1,222.1875	$1,222.18	$1,222.15	$1,222.20