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	$158.30	12.199%	$177.611	$177.61	$177.60	$177.60
Purchase #2	$61.92	5.208%	$65.1448	$65.14	$65.15	$65.10
Purchase #3	$173.70	13.316%	$196.8299	$196.83	$196.85	$196.80
Purchase #4	$216.57	4.597%	$226.5257	$226.53	$226.55	$226.50
Purchase #5	$225.73	13.345%	$255.8537	$255.85	$255.85	$255.90
Purchase #6	$153.64	3.786%	$159.4568	$159.46	$159.45	$159.50
Purchase #7	$197.98	4.140%	$206.1764	$206.18	$206.20	$206.20
7 purchase totals =	$1,187.84		$1,287.5983	$1,287.60	$1,287.65	$1,287.60