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	$232.28	13.363%	$263.3196	$263.32	$263.30	$263.30
Purchase #2	$17.72	13.514%	$20.1147	$20.11	$20.10	$20.10
Purchase #3	$228.73	4.232%	$238.4099	$238.41	$238.40	$238.40
Purchase #4	$174.96	6.345%	$186.0612	$186.06	$186.05	$186.10
Purchase #5	$47.79	5.665%	$50.4973	$50.50	$50.50	$50.50
Purchase #6	$155.88	11.160%	$173.2762	$173.28	$173.30	$173.30
Purchase #7	$176.25	8.810%	$191.7776	$191.78	$191.80	$191.80
7 purchase totals =	$1,033.61		$1,123.4565	$1,123.46	$1,123.45	$1,123.50