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	$133.66	6.580%	$142.4548	$142.45	$142.45	$142.50
Purchase #2	$231.56	9.468%	$253.4841	$253.48	$253.50	$253.50
Purchase #3	$133.32	11.851%	$149.1198	$149.12	$149.10	$149.10
Purchase #4	$143.43	6.395%	$152.6023	$152.60	$152.60	$152.60
Purchase #5	$47.58	6.707%	$50.7712	$50.77	$50.75	$50.80
Purchase #6	$105.98	7.468%	$113.8946	$113.89	$113.90	$113.90
Purchase #7	$74.42	5.857%	$78.7788	$78.78	$78.80	$78.80
7 purchase totals =	$869.95		$941.1056	$941.09	$941.10	$941.20