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	$149.78	13.448%	$169.9224	$169.92	$169.90	$169.90
Purchase #2	$124.43	8.501%	$135.0078	$135.01	$135.00	$135.00
Purchase #3	$154.37	12.348%	$173.4316	$173.43	$173.45	$173.40
Purchase #4	$202.83	13.831%	$230.8834	$230.88	$230.90	$230.90
Purchase #5	$102.44	8.412%	$111.0573	$111.06	$111.05	$111.10
Purchase #6	$149.90	4.179%	$156.1643	$156.16	$156.15	$156.20
Purchase #7	$149.59	3.468%	$154.7778	$154.78	$154.80	$154.80
7 purchase totals =	$1,033.34		$1,131.2446	$1,131.24	$1,131.25	$1,131.30