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	$186.70	5.148%	$196.3113	$196.31	$196.30	$196.30
Purchase #2	$160.58	7.252%	$172.2253	$172.23	$172.25	$172.20
Purchase #3	$231.50	3.866%	$240.4498	$240.45	$240.45	$240.40
Purchase #4	$197.38	8.606%	$214.3665	$214.37	$214.35	$214.40
Purchase #5	$20.40	12.173%	$22.8833	$22.88	$22.90	$22.90
Purchase #6	$51.46	11.151%	$57.1983	$57.20	$57.20	$57.20
Purchase #7	$147.43	8.539%	$160.019	$160.02	$160.00	$160.00
7 purchase totals =	$995.45		$1,063.4535	$1,063.46	$1,063.45	$1,063.40