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	$192.48	10.545%	$212.777	$212.78	$212.80	$212.80
Purchase #2	$173.40	13.114%	$196.1397	$196.14	$196.15	$196.10
Purchase #3	$235.78	7.668%	$253.8596	$253.86	$253.85	$253.90
Purchase #4	$240.52	3.583%	$249.1378	$249.14	$249.15	$249.10
Purchase #5	$134.83	4.224%	$140.5252	$140.53	$140.55	$140.50
Purchase #6	$73.39	4.693%	$76.8342	$76.83	$76.85	$76.80
Purchase #7	$231.79	12.790%	$261.4359	$261.44	$261.45	$261.40
7 purchase totals =	$1,282.19		$1,390.7094	$1,390.72	$1,390.80	$1,390.60