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	$199.68	8.621%	$216.8944	$216.89	$216.90	$216.90
Purchase #2	$89.88	5.759%	$95.0562	$95.06	$95.05	$95.10
Purchase #3	$142.52	13.687%	$162.0267	$162.03	$162.05	$162.00
Purchase #4	$99.60	9.618%	$109.1795	$109.18	$109.20	$109.20
Purchase #5	$26.50	13.577%	$30.0979	$30.10	$30.10	$30.10
Purchase #6	$194.74	8.786%	$211.8499	$211.85	$211.85	$211.80
Purchase #7	$141.71	8.256%	$153.4096	$153.41	$153.40	$153.40
7 purchase totals =	$894.63		$978.5142	$978.52	$978.55	$978.50