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	$71.72	11.255%	$79.7921	$79.79	$79.80	$79.80
Purchase #2	$18.30	6.157%	$19.4267	$19.43	$19.45	$19.40
Purchase #3	$143.89	8.339%	$155.889	$155.89	$155.90	$155.90
Purchase #4	$172.93	3.815%	$179.5273	$179.53	$179.55	$179.50
Purchase #5	$149.54	8.353%	$162.0311	$162.03	$162.05	$162.00
Purchase #6	$78.51	3.858%	$81.5389	$81.54	$81.55	$81.50
Purchase #7	$113.96	11.350%	$126.8945	$126.89	$126.90	$126.90
7 purchase totals =	$748.85		$805.0996	$805.10	$805.20	$805.00