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	$9.30	13.498%	$10.5553	$10.56	$10.55	$10.60
Purchase #2	$17.38	6.784%	$18.5591	$18.56	$18.55	$18.60
Purchase #3	$6.37	7.238%	$6.8311	$6.83	$6.85	$6.80
Purchase #4	$201.67	4.852%	$211.455	$211.46	$211.45	$211.50
Purchase #5	$172.76	9.335%	$188.8871	$188.89	$188.90	$188.90
Purchase #6	$122.52	4.284%	$127.7688	$127.77	$127.75	$127.80
Purchase #7	$112.40	9.318%	$122.8734	$122.87	$122.85	$122.90
7 purchase totals =	$642.40		$686.9298	$686.94	$686.90	$687.10