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	$233.85	5.121%	$245.8255	$245.83	$245.85	$245.80
Purchase #2	$113.61	13.255%	$128.669	$128.67	$128.65	$128.70
Purchase #3	$101.46	12.110%	$113.7468	$113.75	$113.75	$113.70
Purchase #4	$64.63	12.820%	$72.9156	$72.92	$72.90	$72.90
Purchase #5	$123.37	10.714%	$136.5879	$136.59	$136.60	$136.60
Purchase #6	$89.36	12.569%	$100.5917	$100.59	$100.60	$100.60
Purchase #7	$144.36	6.117%	$153.1905	$153.19	$153.20	$153.20
7 purchase totals =	$870.64		$951.5270	$951.54	$951.55	$951.50