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	$59.33	13.508%	$67.3443	$67.34	$67.35	$67.30
Purchase #2	$156.26	10.267%	$172.3032	$172.30	$172.30	$172.30
Purchase #3	$134.70	9.353%	$147.2985	$147.30	$147.30	$147.30
Purchase #4	$161.28	6.759%	$172.1809	$172.18	$172.20	$172.20
Purchase #5	$214.34	13.738%	$243.786	$243.79	$243.80	$243.80
Purchase #6	$237.25	7.414%	$254.8397	$254.84	$254.85	$254.80
Purchase #7	$105.85	4.708%	$110.8334	$110.83	$110.85	$110.80
7 purchase totals =	$1,069.01		$1,168.5860	$1,168.58	$1,168.65	$1,168.50