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	$192.86	9.717%	$211.6002	$211.60	$211.60	$211.60
Purchase #2	$104.75	8.188%	$113.3269	$113.33	$113.35	$113.30
Purchase #3	$160.26	7.431%	$172.1689	$172.17	$172.15	$172.20
Purchase #4	$62.70	10.555%	$69.318	$69.32	$69.30	$69.30
Purchase #5	$147.45	13.790%	$167.7834	$167.78	$167.80	$167.80
Purchase #6	$105.64	5.633%	$111.5907	$111.59	$111.60	$111.60
Purchase #7	$122.50	4.508%	$128.0223	$128.02	$128.00	$128.00
7 purchase totals =	$896.16		$973.8104	$973.81	$973.80	$973.80