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	$95.89	5.531%	$101.1937	$101.19	$101.20	$101.20
Purchase #2	$25.39	13.521%	$28.823	$28.82	$28.80	$28.80
Purchase #3	$48.68	12.463%	$54.747	$54.75	$54.75	$54.70
Purchase #4	$85.82	6.365%	$91.2824	$91.28	$91.30	$91.30
Purchase #5	$30.26	4.113%	$31.5046	$31.50	$31.50	$31.50
Purchase #6	$36.28	12.353%	$40.7617	$40.76	$40.75	$40.80
Purchase #7	$225.77	3.539%	$233.76	$233.76	$233.75	$233.80
7 purchase totals =	$548.09		$582.0724	$582.06	$582.05	$582.10