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	$131.54	13.387%	$149.1493	$149.15	$149.15	$149.10
Purchase #2	$165.82	4.576%	$173.4079	$173.41	$173.40	$173.40
Purchase #3	$132.51	11.761%	$148.0945	$148.09	$148.10	$148.10
Purchase #4	$191.83	8.192%	$207.5447	$207.54	$207.55	$207.50
Purchase #5	$40.76	6.189%	$43.2826	$43.28	$43.30	$43.30
Purchase #6	$72.38	8.132%	$78.2659	$78.27	$78.25	$78.30
Purchase #7	$59.73	3.660%	$61.9161	$61.92	$61.90	$61.90
7 purchase totals =	$794.57		$861.6610	$861.66	$861.65	$861.60