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	$218.86	5.487%	$230.8688	$230.87	$230.85	$230.90
Purchase #2	$134.48	4.133%	$140.0381	$140.04	$140.05	$140.00
Purchase #3	$143.82	6.347%	$152.9483	$152.95	$152.95	$152.90
Purchase #4	$128.90	12.316%	$144.7753	$144.78	$144.80	$144.80
Purchase #5	$87.75	3.627%	$90.9327	$90.93	$90.95	$90.90
Purchase #6	$87.95	8.689%	$95.592	$95.59	$95.60	$95.60
Purchase #7	$53.27	8.399%	$57.7441	$57.74	$57.75	$57.70
7 purchase totals =	$855.03		$912.8993	$912.90	$912.95	$912.80