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	$191.25	12.366%	$214.9	$214.90	$214.90	$214.90
Purchase #2	$109.76	3.390%	$113.4809	$113.48	$113.50	$113.50
Purchase #3	$26.32	8.703%	$28.6106	$28.61	$28.60	$28.60
Purchase #4	$47.27	6.479%	$50.3326	$50.33	$50.35	$50.30
Purchase #5	$203.69	13.128%	$230.4304	$230.43	$230.45	$230.40
Purchase #6	$145.96	12.574%	$164.313	$164.31	$164.30	$164.30
Purchase #7	$83.56	6.565%	$89.0457	$89.05	$89.05	$89.00
7 purchase totals =	$807.81		$891.1132	$891.11	$891.15	$891.00