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	$160.42	13.194%	$181.5858	$181.59	$181.60	$181.60
Purchase #2	$220.98	5.659%	$233.4853	$233.49	$233.50	$233.50
Purchase #3	$237.96	13.383%	$269.8062	$269.81	$269.80	$269.80
Purchase #4	$249.34	4.350%	$260.1863	$260.19	$260.20	$260.20
Purchase #5	$149.78	6.513%	$159.5352	$159.54	$159.55	$159.50
Purchase #6	$58.78	13.773%	$66.8758	$66.88	$66.90	$66.90
Purchase #7	$69.57	4.357%	$72.6012	$72.60	$72.60	$72.60
7 purchase totals =	$1,146.83		$1,244.0758	$1,244.10	$1,244.15	$1,244.10