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	$85.77	7.874%	$92.5235	$92.52	$92.50	$92.50
Purchase #2	$61.82	13.778%	$70.3376	$70.34	$70.35	$70.30
Purchase #3	$161.49	10.239%	$178.025	$178.03	$178.05	$178.00
Purchase #4	$79.48	7.343%	$85.3162	$85.32	$85.30	$85.30
Purchase #5	$13.46	7.239%	$14.4344	$14.43	$14.45	$14.40
Purchase #6	$62.76	6.451%	$66.8086	$66.81	$66.80	$66.80
Purchase #7	$100.60	4.190%	$104.8151	$104.82	$104.80	$104.80
7 purchase totals =	$565.38		$612.2604	$612.27	$612.25	$612.10