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	$26.58	10.741%	$29.435	$29.44	$29.45	$29.40
Purchase #2	$72.73	6.475%	$77.4393	$77.44	$77.45	$77.40
Purchase #3	$32.71	10.470%	$36.1347	$36.13	$36.15	$36.10
Purchase #4	$34.28	13.244%	$38.82	$38.82	$38.80	$38.80
Purchase #5	$108.72	13.811%	$123.7353	$123.74	$123.75	$123.70
Purchase #6	$48.77	9.323%	$53.3168	$53.32	$53.30	$53.30
Purchase #7	$154.25	9.763%	$169.3094	$169.31	$169.30	$169.30
7 purchase totals =	$478.04		$528.1905	$528.20	$528.20	$528.00