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	$175.61	7.588%	$188.9353	$188.94	$188.95	$188.90
Purchase #2	$203.49	9.631%	$223.0881	$223.09	$223.10	$223.10
Purchase #3	$194.50	8.256%	$210.5579	$210.56	$210.55	$210.60
Purchase #4	$104.61	6.376%	$111.2799	$111.28	$111.30	$111.30
Purchase #5	$102.51	7.427%	$110.1234	$110.12	$110.10	$110.10
Purchase #6	$152.33	13.162%	$172.3797	$172.38	$172.40	$172.40
Purchase #7	$19.65	3.754%	$20.3877	$20.39	$20.40	$20.40
7 purchase totals =	$952.70		$1,036.7520	$1,036.76	$1,036.80	$1,036.80