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	$206.30	4.257%	$215.0822	$215.08	$215.10	$215.10
Purchase #2	$36.41	11.779%	$40.6987	$40.70	$40.70	$40.70
Purchase #3	$17.67	4.179%	$18.4084	$18.41	$18.40	$18.40
Purchase #4	$58.65	5.761%	$62.0288	$62.03	$62.05	$62.00
Purchase #5	$42.58	5.830%	$45.0624	$45.06	$45.05	$45.10
Purchase #6	$11.58	8.783%	$12.5971	$12.60	$12.60	$12.60
Purchase #7	$39.86	6.312%	$42.376	$42.38	$42.40	$42.40
7 purchase totals =	$413.05		$436.2536	$436.26	$436.30	$436.30