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	$146.81	8.123%	$158.7354	$158.74	$158.75	$158.70
Purchase #2	$45.89	7.611%	$49.3827	$49.38	$49.40	$49.40
Purchase #3	$150.54	6.628%	$160.5178	$160.52	$160.50	$160.50
Purchase #4	$107.40	5.298%	$113.0901	$113.09	$113.10	$113.10
Purchase #5	$245.90	3.684%	$254.959	$254.96	$254.95	$255.00
Purchase #6	$146.98	5.619%	$155.2388	$155.24	$155.25	$155.20
Purchase #7	$161.88	11.549%	$180.5755	$180.58	$180.60	$180.60
7 purchase totals =	$1,005.40		$1,072.4993	$1,072.51	$1,072.55	$1,072.50