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	$58.59	9.724%	$64.2873	$64.29	$64.30	$64.30
Purchase #2	$175.49	7.633%	$188.8852	$188.89	$188.90	$188.90
Purchase #3	$52.92	4.484%	$55.2929	$55.29	$55.30	$55.30
Purchase #4	$158.42	13.563%	$179.9065	$179.91	$179.90	$179.90
Purchase #5	$85.32	11.223%	$94.8955	$94.90	$94.90	$94.90
Purchase #6	$169.33	11.514%	$188.8267	$188.83	$188.85	$188.80
Purchase #7	$105.53	7.693%	$113.6484	$113.65	$113.65	$113.60
7 purchase totals =	$805.60		$885.7425	$885.76	$885.80	$885.70