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	$177.28	4.368%	$185.0236	$185.02	$185.00	$185.00
Purchase #2	$188.46	6.394%	$200.5101	$200.51	$200.50	$200.50
Purchase #3	$118.66	4.571%	$124.0839	$124.08	$124.10	$124.10
Purchase #4	$159.59	8.774%	$173.5924	$173.59	$173.60	$173.60
Purchase #5	$24.51	13.830%	$27.8997	$27.90	$27.90	$27.90
Purchase #6	$93.34	9.645%	$102.3426	$102.34	$102.35	$102.30
Purchase #7	$48.78	9.538%	$53.4326	$53.43	$53.45	$53.40
7 purchase totals =	$810.62		$866.8849	$866.87	$866.90	$866.80