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	$136.77	10.662%	$151.3524	$151.35	$151.35	$151.40
Purchase #2	$240.44	3.103%	$247.9009	$247.90	$247.90	$247.90
Purchase #3	$53.74	10.833%	$59.5617	$59.56	$59.55	$59.60
Purchase #4	$107.55	3.544%	$111.3616	$111.36	$111.35	$111.40
Purchase #5	$226.29	7.150%	$242.4697	$242.47	$242.45	$242.50
Purchase #6	$239.40	8.573%	$259.9238	$259.92	$259.90	$259.90
Purchase #7	$227.87	6.732%	$243.2102	$243.21	$243.20	$243.20
7 purchase totals =	$1,232.06		$1,315.7803	$1,315.77	$1,315.70	$1,315.90