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	$130.88	9.839%	$143.7573	$143.76	$143.75	$143.80
Purchase #2	$105.62	5.312%	$111.2305	$111.23	$111.25	$111.20
Purchase #3	$215.78	11.130%	$239.7963	$239.80	$239.80	$239.80
Purchase #4	$130.50	9.509%	$142.9092	$142.91	$142.90	$142.90
Purchase #5	$173.76	7.690%	$187.1221	$187.12	$187.10	$187.10
Purchase #6	$152.28	5.184%	$160.1742	$160.17	$160.15	$160.20
Purchase #7	$191.91	7.125%	$205.5836	$205.58	$205.60	$205.60
7 purchase totals =	$1,100.73		$1,190.5732	$1,190.57	$1,190.55	$1,190.60