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	$171.83	12.805%	$193.8328	$193.83	$193.85	$193.80
Purchase #2	$37.28	8.764%	$40.5472	$40.55	$40.55	$40.50
Purchase #3	$132.67	9.385%	$145.1211	$145.12	$145.10	$145.10
Purchase #4	$167.45	8.130%	$181.0637	$181.06	$181.05	$181.10
Purchase #5	$118.55	11.113%	$131.7245	$131.72	$131.70	$131.70
Purchase #6	$110.43	7.480%	$118.6902	$118.69	$118.70	$118.70
Purchase #7	$66.74	7.263%	$71.5873	$71.59	$71.60	$71.60
7 purchase totals =	$804.95		$882.5668	$882.56	$882.55	$882.50