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	$176.40	6.655%	$188.1394	$188.14	$188.15	$188.10
Purchase #2	$164.91	6.428%	$175.5104	$175.51	$175.50	$175.50
Purchase #3	$188.60	8.454%	$204.5442	$204.54	$204.55	$204.50
Purchase #4	$45.45	9.454%	$49.7468	$49.75	$49.75	$49.70
Purchase #5	$86.27	4.678%	$90.3057	$90.31	$90.30	$90.30
Purchase #6	$53.29	11.850%	$59.6049	$59.60	$59.60	$59.60
Purchase #7	$120.99	7.625%	$130.2155	$130.22	$130.20	$130.20
7 purchase totals =	$835.91		$898.0669	$898.07	$898.05	$897.90