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	$148.91	6.755%	$158.9689	$158.97	$158.95	$159.00
Purchase #2	$165.85	5.614%	$175.1608	$175.16	$175.15	$175.20
Purchase #3	$232.81	10.124%	$256.3797	$256.38	$256.40	$256.40
Purchase #4	$153.77	12.268%	$172.6345	$172.63	$172.65	$172.60
Purchase #5	$104.38	6.632%	$111.3025	$111.30	$111.30	$111.30
Purchase #6	$142.83	7.435%	$153.4494	$153.45	$153.45	$153.40
Purchase #7	$87.91	5.520%	$92.7626	$92.76	$92.75	$92.80
7 purchase totals =	$1,036.46		$1,120.6584	$1,120.65	$1,120.65	$1,120.70