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	$97.52	6.510%	$103.8686	$103.87	$103.85	$103.90
Purchase #2	$160.47	3.251%	$165.6869	$165.69	$165.70	$165.70
Purchase #3	$28.69	11.225%	$31.9105	$31.91	$31.90	$31.90
Purchase #4	$38.32	8.783%	$41.6856	$41.69	$41.70	$41.70
Purchase #5	$69.29	7.412%	$74.4258	$74.43	$74.45	$74.40
Purchase #6	$84.82	9.107%	$92.5446	$92.54	$92.55	$92.50
Purchase #7	$58.90	6.243%	$62.5771	$62.58	$62.60	$62.60
7 purchase totals =	$538.01		$572.6991	$572.71	$572.75	$572.70