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	$224.32	5.796%	$237.3216	$237.32	$237.30	$237.30
Purchase #2	$206.58	6.741%	$220.5056	$220.51	$220.50	$220.50
Purchase #3	$227.26	7.685%	$244.7249	$244.72	$244.70	$244.70
Purchase #4	$40.33	13.721%	$45.8637	$45.86	$45.85	$45.90
Purchase #5	$149.78	9.593%	$164.1484	$164.15	$164.15	$164.10
Purchase #6	$112.80	9.776%	$123.8273	$123.83	$123.85	$123.80
Purchase #7	$192.51	12.784%	$217.1205	$217.12	$217.10	$217.10
7 purchase totals =	$1,153.58		$1,253.5120	$1,253.51	$1,253.45	$1,253.40