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	$9.97	9.182%	$10.8854	$10.89	$10.90	$10.90
Purchase #2	$39.28	6.406%	$41.7963	$41.80	$41.80	$41.80
Purchase #3	$151.40	3.271%	$156.3523	$156.35	$156.35	$156.40
Purchase #4	$181.53	5.706%	$191.8881	$191.89	$191.90	$191.90
Purchase #5	$207.89	13.472%	$235.8969	$235.90	$235.90	$235.90
Purchase #6	$153.28	3.280%	$158.3076	$158.31	$158.30	$158.30
Purchase #7	$71.62	6.642%	$76.377	$76.38	$76.40	$76.40
7 purchase totals =	$814.97		$871.5036	$871.52	$871.55	$871.60