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	$99.98	11.800%	$111.7776	$111.78	$111.80	$111.80
Purchase #2	$208.48	10.633%	$230.6477	$230.65	$230.65	$230.60
Purchase #3	$46.48	13.544%	$52.7753	$52.78	$52.80	$52.80
Purchase #4	$192.76	12.655%	$217.1538	$217.15	$217.15	$217.20
Purchase #5	$87.64	4.307%	$91.4147	$91.41	$91.40	$91.40
Purchase #6	$152.48	10.492%	$168.4782	$168.48	$168.50	$168.50
Purchase #7	$208.73	11.786%	$233.3309	$233.33	$233.35	$233.30
7 purchase totals =	$996.55		$1,105.5782	$1,105.58	$1,105.65	$1,105.60