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	$198.97	11.773%	$222.3947	$222.39	$222.40	$222.40
Purchase #2	$249.26	11.238%	$277.2718	$277.27	$277.25	$277.30
Purchase #3	$113.25	7.481%	$121.7222	$121.72	$121.70	$121.70
Purchase #4	$137.25	10.189%	$151.2344	$151.23	$151.25	$151.20
Purchase #5	$245.78	7.337%	$263.8129	$263.81	$263.80	$263.80
Purchase #6	$10.34	5.761%	$10.9357	$10.94	$10.95	$10.90
Purchase #7	$113.55	12.211%	$127.4156	$127.42	$127.40	$127.40
7 purchase totals =	$1,068.40		$1,174.7873	$1,174.78	$1,174.75	$1,174.70