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	$219.50	8.568%	$238.3068	$238.31	$238.30	$238.30
Purchase #2	$59.77	13.827%	$68.0344	$68.03	$68.05	$68.00
Purchase #3	$42.31	11.382%	$47.1257	$47.13	$47.15	$47.10
Purchase #4	$96.52	7.387%	$103.6499	$103.65	$103.65	$103.60
Purchase #5	$235.92	6.608%	$251.5096	$251.51	$251.50	$251.50
Purchase #6	$62.89	7.171%	$67.3998	$67.40	$67.40	$67.40
Purchase #7	$92.93	8.209%	$100.5586	$100.56	$100.55	$100.60
7 purchase totals =	$809.84		$876.5848	$876.59	$876.60	$876.50