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	$81.91	6.461%	$87.2022	$87.20	$87.20	$87.20
Purchase #2	$61.62	9.460%	$67.4493	$67.45	$67.45	$67.40
Purchase #3	$59.44	3.140%	$61.3064	$61.31	$61.30	$61.30
Purchase #4	$10.51	13.316%	$11.9095	$11.91	$11.90	$11.90
Purchase #5	$224.48	13.185%	$254.0777	$254.08	$254.10	$254.10
Purchase #6	$160.72	6.685%	$171.4641	$171.46	$171.45	$171.50
Purchase #7	$175.34	3.375%	$181.2577	$181.26	$181.25	$181.30
7 purchase totals =	$774.02		$834.6669	$834.67	$834.65	$834.70