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	$107.42	3.692%	$111.3859	$111.39	$111.40	$111.40
Purchase #2	$202.44	9.810%	$222.2994	$222.30	$222.30	$222.30
Purchase #3	$57.50	6.539%	$61.2599	$61.26	$61.25	$61.30
Purchase #4	$203.62	10.870%	$225.7535	$225.75	$225.75	$225.80
Purchase #5	$48.25	11.301%	$53.7027	$53.70	$53.70	$53.70
Purchase #6	$166.74	4.422%	$174.1132	$174.11	$174.10	$174.10
Purchase #7	$149.30	12.310%	$167.6788	$167.68	$167.70	$167.70
7 purchase totals =	$935.27		$1,016.1934	$1,016.19	$1,016.20	$1,016.30