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	$130.97	10.601%	$144.8541	$144.85	$144.85	$144.90
Purchase #2	$41.85	5.114%	$43.9902	$43.99	$44.00	$44.00
Purchase #3	$65.80	4.129%	$68.5169	$68.52	$68.50	$68.50
Purchase #4	$128.82	12.355%	$144.7357	$144.74	$144.75	$144.70
Purchase #5	$145.48	13.601%	$165.2667	$165.27	$165.25	$165.30
Purchase #6	$165.82	4.228%	$172.8309	$172.83	$172.85	$172.80
Purchase #7	$113.78	12.764%	$128.3029	$128.30	$128.30	$128.30
7 purchase totals =	$792.52		$868.4974	$868.50	$868.50	$868.50