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	$91.75	8.353%	$99.4139	$99.41	$99.40	$99.40
Purchase #2	$184.83	3.148%	$190.6484	$190.65	$190.65	$190.60
Purchase #3	$104.84	11.244%	$116.6282	$116.63	$116.65	$116.60
Purchase #4	$172.93	13.717%	$196.6508	$196.65	$196.65	$196.70
Purchase #5	$89.42	4.194%	$93.1703	$93.17	$93.15	$93.20
Purchase #6	$97.36	11.497%	$108.5535	$108.55	$108.55	$108.60
Purchase #7	$142.96	11.595%	$159.5362	$159.54	$159.55	$159.50
7 purchase totals =	$884.09		$964.6013	$964.60	$964.60	$964.60