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	$53.59	11.640%	$59.8279	$59.83	$59.85	$59.80
Purchase #2	$53.28	8.579%	$57.8509	$57.85	$57.85	$57.90
Purchase #3	$233.85	7.414%	$251.1876	$251.19	$251.20	$251.20
Purchase #4	$247.31	5.242%	$260.274	$260.27	$260.25	$260.30
Purchase #5	$174.88	11.578%	$195.1276	$195.13	$195.15	$195.10
Purchase #6	$210.26	11.468%	$234.3726	$234.37	$234.35	$234.40
Purchase #7	$95.83	5.161%	$100.7758	$100.78	$100.80	$100.80
7 purchase totals =	$1,069.00		$1,159.4164	$1,159.42	$1,159.45	$1,159.50