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	$57.59	5.335%	$60.6624	$60.66	$60.65	$60.70
Purchase #2	$64.65	12.599%	$72.7953	$72.80	$72.80	$72.80
Purchase #3	$229.87	11.458%	$256.2085	$256.21	$256.20	$256.20
Purchase #4	$77.53	10.659%	$85.7939	$85.79	$85.80	$85.80
Purchase #5	$38.66	6.786%	$41.2835	$41.28	$41.30	$41.30
Purchase #6	$77.57	13.789%	$88.2661	$88.27	$88.25	$88.30
Purchase #7	$150.33	5.189%	$158.1306	$158.13	$158.15	$158.10
7 purchase totals =	$696.20		$763.1403	$763.14	$763.15	$763.20