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	$12.88	11.723%	$14.3899	$14.39	$14.40	$14.40
Purchase #2	$40.60	6.598%	$43.2788	$43.28	$43.30	$43.30
Purchase #3	$225.65	8.744%	$245.3808	$245.38	$245.40	$245.40
Purchase #4	$64.54	10.577%	$71.3664	$71.37	$71.35	$71.40
Purchase #5	$21.39	4.147%	$22.277	$22.28	$22.30	$22.30
Purchase #6	$19.64	4.858%	$20.5941	$20.59	$20.60	$20.60
Purchase #7	$99.72	11.644%	$111.3314	$111.33	$111.35	$111.30
7 purchase totals =	$484.42		$528.6184	$528.62	$528.70	$528.70