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	$154.76	6.732%	$165.1784	$165.18	$165.20	$165.20
Purchase #2	$79.56	3.190%	$82.098	$82.10	$82.10	$82.10
Purchase #3	$231.39	5.762%	$244.7227	$244.72	$244.70	$244.70
Purchase #4	$100.91	6.323%	$107.2905	$107.29	$107.30	$107.30
Purchase #5	$230.59	10.845%	$255.5975	$255.60	$255.60	$255.60
Purchase #6	$55.73	3.656%	$57.7675	$57.77	$57.75	$57.80
Purchase #7	$217.76	11.547%	$242.9047	$242.90	$242.90	$242.90
7 purchase totals =	$1,070.70		$1,155.5593	$1,155.56	$1,155.55	$1,155.60