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	$146.49	4.162%	$152.5869	$152.59	$152.60	$152.60
Purchase #2	$175.82	5.495%	$185.4813	$185.48	$185.50	$185.50
Purchase #3	$50.33	7.281%	$53.9945	$53.99	$54.00	$54.00
Purchase #4	$174.41	3.125%	$179.8603	$179.86	$179.85	$179.90
Purchase #5	$182.97	5.176%	$192.4405	$192.44	$192.45	$192.40
Purchase #6	$204.70	6.491%	$217.9871	$217.99	$218.00	$218.00
Purchase #7	$79.32	5.213%	$83.455	$83.46	$83.45	$83.50
7 purchase totals =	$1,014.04		$1,065.8056	$1,065.81	$1,065.85	$1,065.90