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	$136.31	7.809%	$146.9544	$146.95	$146.95	$147.00
Purchase #2	$122.41	13.604%	$139.0627	$139.06	$139.05	$139.10
Purchase #3	$137.89	5.279%	$145.1692	$145.17	$145.15	$145.20
Purchase #4	$209.90	3.832%	$217.9434	$217.94	$217.95	$217.90
Purchase #5	$19.29	6.510%	$20.5458	$20.55	$20.55	$20.50
Purchase #6	$223.27	8.103%	$241.3616	$241.36	$241.35	$241.40
Purchase #7	$219.75	7.618%	$236.4906	$236.49	$236.50	$236.50
7 purchase totals =	$1,068.82		$1,147.5277	$1,147.52	$1,147.50	$1,147.60