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	$164.52	4.541%	$171.9909	$171.99	$172.00	$172.00
Purchase #2	$40.45	3.698%	$41.9458	$41.95	$41.95	$41.90
Purchase #3	$85.45	12.675%	$96.2808	$96.28	$96.30	$96.30
Purchase #4	$35.73	5.673%	$37.757	$37.76	$37.75	$37.80
Purchase #5	$168.26	13.430%	$190.8573	$190.86	$190.85	$190.90
Purchase #6	$105.79	5.401%	$111.5037	$111.50	$111.50	$111.50
Purchase #7	$159.28	4.729%	$166.8124	$166.81	$166.80	$166.80
7 purchase totals =	$759.48		$817.1479	$817.15	$817.15	$817.20