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	$100.45	4.539%	$105.0094	$105.01	$105.00	$105.00
Purchase #2	$121.26	13.530%	$137.6665	$137.67	$137.65	$137.70
Purchase #3	$100.49	3.618%	$104.1257	$104.13	$104.15	$104.10
Purchase #4	$166.76	10.578%	$184.3999	$184.40	$184.40	$184.40
Purchase #5	$137.44	11.516%	$153.2676	$153.27	$153.25	$153.30
Purchase #6	$249.99	10.267%	$275.6565	$275.66	$275.65	$275.70
Purchase #7	$117.98	6.865%	$126.0793	$126.08	$126.10	$126.10
7 purchase totals =	$994.37		$1,086.2049	$1,086.22	$1,086.20	$1,086.30