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	$10.41	12.667%	$11.7286	$11.73	$11.75	$11.70
Purchase #2	$118.69	7.301%	$127.3556	$127.36	$127.35	$127.40
Purchase #3	$187.96	7.819%	$202.6566	$202.66	$202.65	$202.70
Purchase #4	$151.67	9.704%	$166.3881	$166.39	$166.40	$166.40
Purchase #5	$49.78	13.427%	$56.464	$56.46	$56.45	$56.50
Purchase #6	$233.79	13.584%	$265.548	$265.55	$265.55	$265.50
Purchase #7	$223.27	3.571%	$231.243	$231.24	$231.25	$231.20
7 purchase totals =	$975.57		$1,061.3839	$1,061.39	$1,061.40	$1,061.40