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	$191.85	9.620%	$210.306	$210.31	$210.30	$210.30
Purchase #2	$222.82	9.853%	$244.7745	$244.77	$244.75	$244.80
Purchase #3	$217.32	7.480%	$233.5755	$233.58	$233.60	$233.60
Purchase #4	$162.79	7.870%	$175.6016	$175.60	$175.60	$175.60
Purchase #5	$51.36	8.149%	$55.5453	$55.55	$55.55	$55.50
Purchase #6	$27.91	13.415%	$31.6541	$31.65	$31.65	$31.70
Purchase #7	$165.58	11.761%	$185.0539	$185.05	$185.05	$185.10
7 purchase totals =	$1,039.63		$1,136.5109	$1,136.51	$1,136.50	$1,136.60