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	$172.83	3.843%	$179.4719	$179.47	$179.45	$179.50
Purchase #2	$173.76	7.818%	$187.3446	$187.34	$187.35	$187.30
Purchase #3	$122.60	6.252%	$130.265	$130.27	$130.25	$130.30
Purchase #4	$175.39	13.146%	$198.4468	$198.45	$198.45	$198.40
Purchase #5	$250.87	4.789%	$262.8842	$262.88	$262.90	$262.90
Purchase #6	$117.34	9.648%	$128.661	$128.66	$128.65	$128.70
Purchase #7	$83.41	5.738%	$88.1961	$88.20	$88.20	$88.20
7 purchase totals =	$1,096.20		$1,175.2696	$1,175.27	$1,175.25	$1,175.30