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	$135.41	6.682%	$144.4581	$144.46	$144.45	$144.50
Purchase #2	$175.89	5.788%	$186.0705	$186.07	$186.05	$186.10
Purchase #3	$230.29	5.448%	$242.8362	$242.84	$242.85	$242.80
Purchase #4	$242.28	13.287%	$274.4717	$274.47	$274.45	$274.50
Purchase #5	$249.90	6.612%	$266.4234	$266.42	$266.40	$266.40
Purchase #6	$98.42	4.837%	$103.1806	$103.18	$103.20	$103.20
Purchase #7	$241.28	12.259%	$270.8585	$270.86	$270.85	$270.90
7 purchase totals =	$1,373.47		$1,488.2990	$1,488.30	$1,488.25	$1,488.40