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	$173.52	12.721%	$195.5935	$195.59	$195.60	$195.60
Purchase #2	$231.72	8.178%	$250.6701	$250.67	$250.65	$250.70
Purchase #3	$186.59	8.133%	$201.7654	$201.77	$201.75	$201.80
Purchase #4	$215.86	6.118%	$229.0663	$229.07	$229.05	$229.10
Purchase #5	$121.91	3.738%	$126.467	$126.47	$126.45	$126.50
Purchase #6	$174.82	6.231%	$185.713	$185.71	$185.70	$185.70
Purchase #7	$6.58	13.337%	$7.4576	$7.46	$7.45	$7.50
7 purchase totals =	$1,111.00		$1,196.7329	$1,196.74	$1,196.65	$1,196.90