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	$54.86	11.673%	$61.2638	$61.26	$61.25	$61.30
Purchase #2	$30.81	4.411%	$32.169	$32.17	$32.15	$32.20
Purchase #3	$150.88	5.771%	$159.5873	$159.59	$159.60	$159.60
Purchase #4	$147.56	6.112%	$156.5789	$156.58	$156.60	$156.60
Purchase #5	$158.65	5.811%	$167.8692	$167.87	$167.85	$167.90
Purchase #6	$30.62	9.844%	$33.6342	$33.63	$33.65	$33.60
Purchase #7	$221.86	13.245%	$251.2454	$251.25	$251.25	$251.20
7 purchase totals =	$795.24		$862.3478	$862.35	$862.35	$862.40