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	$184.87	12.663%	$208.2801	$208.28	$208.30	$208.30
Purchase #2	$13.63	6.509%	$14.5172	$14.52	$14.50	$14.50
Purchase #3	$114.38	11.784%	$127.8585	$127.86	$127.85	$127.90
Purchase #4	$204.43	5.550%	$215.7759	$215.78	$215.80	$215.80
Purchase #5	$89.54	3.858%	$92.9945	$92.99	$93.00	$93.00
Purchase #6	$36.32	3.346%	$37.5353	$37.54	$37.55	$37.50
Purchase #7	$17.51	6.490%	$18.6464	$18.65	$18.65	$18.60
7 purchase totals =	$660.68		$715.6079	$715.62	$715.65	$715.60