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	$130.85	11.168%	$145.4633	$145.46	$145.45	$145.50
Purchase #2	$118.74	4.145%	$123.6618	$123.66	$123.65	$123.70
Purchase #3	$241.51	7.189%	$258.8722	$258.87	$258.85	$258.90
Purchase #4	$241.51	9.676%	$264.8785	$264.88	$264.90	$264.90
Purchase #5	$130.40	5.613%	$137.7194	$137.72	$137.70	$137.70
Purchase #6	$161.89	8.275%	$175.2864	$175.29	$175.30	$175.30
Purchase #7	$210.86	13.216%	$238.7273	$238.73	$238.75	$238.70
7 purchase totals =	$1,235.76		$1,344.6089	$1,344.61	$1,344.60	$1,344.70