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	$39.96	8.632%	$43.4093	$43.41	$43.40	$43.40
Purchase #2	$235.83	11.276%	$262.4222	$262.42	$262.40	$262.40
Purchase #3	$188.70	6.422%	$200.8183	$200.82	$200.80	$200.80
Purchase #4	$69.37	11.562%	$77.3906	$77.39	$77.40	$77.40
Purchase #5	$223.70	4.191%	$233.0753	$233.08	$233.10	$233.10
Purchase #6	$151.57	9.574%	$166.0813	$166.08	$166.10	$166.10
Purchase #7	$181.28	11.607%	$202.3212	$202.32	$202.30	$202.30
7 purchase totals =	$1,090.41		$1,185.5182	$1,185.52	$1,185.50	$1,185.50