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	$117.35	4.314%	$122.4125	$122.41	$122.40	$122.40
Purchase #2	$166.68	7.843%	$179.7527	$179.75	$179.75	$179.80
Purchase #3	$37.62	6.641%	$40.1183	$40.12	$40.10	$40.10
Purchase #4	$109.28	5.480%	$115.2685	$115.27	$115.25	$115.30
Purchase #5	$136.58	5.805%	$144.5085	$144.51	$144.50	$144.50
Purchase #6	$40.78	6.603%	$43.4727	$43.47	$43.45	$43.50
Purchase #7	$83.90	7.461%	$90.1598	$90.16	$90.15	$90.20
7 purchase totals =	$692.19		$735.6930	$735.69	$735.60	$735.80