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	$82.87	11.193%	$92.1456	$92.15	$92.15	$92.10
Purchase #2	$19.86	9.385%	$21.7239	$21.72	$21.70	$21.70
Purchase #3	$49.85	9.492%	$54.5818	$54.58	$54.60	$54.60
Purchase #4	$94.95	9.490%	$103.9608	$103.96	$103.95	$104.00
Purchase #5	$45.74	6.400%	$48.6674	$48.67	$48.65	$48.70
Purchase #6	$234.66	9.239%	$256.3402	$256.34	$256.35	$256.30
Purchase #7	$18.58	13.395%	$21.0688	$21.07	$21.05	$21.10
7 purchase totals =	$546.51		$598.4885	$598.49	$598.45	$598.50