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	$117.61	12.709%	$132.5571	$132.56	$132.55	$132.60
Purchase #2	$127.71	5.194%	$134.3433	$134.34	$134.35	$134.30
Purchase #3	$122.57	6.234%	$130.211	$130.21	$130.20	$130.20
Purchase #4	$123.30	3.335%	$127.4121	$127.41	$127.40	$127.40
Purchase #5	$139.47	8.765%	$151.6945	$151.69	$151.70	$151.70
Purchase #6	$90.90	4.228%	$94.7433	$94.74	$94.75	$94.70
Purchase #7	$52.80	5.377%	$55.6391	$55.64	$55.65	$55.60
7 purchase totals =	$774.36		$826.6004	$826.59	$826.60	$826.50