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	$83.94	13.107%	$94.942	$94.94	$94.95	$94.90
Purchase #2	$51.56	3.348%	$53.2862	$53.29	$53.30	$53.30
Purchase #3	$157.27	6.493%	$167.4815	$167.48	$167.50	$167.50
Purchase #4	$46.87	7.604%	$50.434	$50.43	$50.45	$50.40
Purchase #5	$63.40	4.467%	$66.2321	$66.23	$66.25	$66.20
Purchase #6	$130.26	9.670%	$142.8561	$142.86	$142.85	$142.90
Purchase #7	$242.47	3.277%	$250.4157	$250.42	$250.40	$250.40
7 purchase totals =	$775.77		$825.6476	$825.65	$825.70	$825.60