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	$223.63	7.705%	$240.8607	$240.86	$240.85	$240.90
Purchase #2	$184.68	4.198%	$192.4329	$192.43	$192.45	$192.40
Purchase #3	$246.51	7.305%	$264.5176	$264.52	$264.50	$264.50
Purchase #4	$102.65	3.480%	$106.2222	$106.22	$106.20	$106.20
Purchase #5	$43.41	13.530%	$49.2834	$49.28	$49.30	$49.30
Purchase #6	$111.80	13.225%	$126.5856	$126.59	$126.60	$126.60
Purchase #7	$152.29	12.860%	$171.8745	$171.87	$171.85	$171.90
7 purchase totals =	$1,064.97		$1,151.7769	$1,151.77	$1,151.75	$1,151.80