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	$240.65	5.703%	$254.3743	$254.37	$254.35	$254.40
Purchase #2	$93.50	11.123%	$103.9	$103.90	$103.90	$103.90
Purchase #3	$200.31	11.151%	$222.6466	$222.65	$222.65	$222.60
Purchase #4	$30.33	13.166%	$34.3232	$34.32	$34.30	$34.30
Purchase #5	$189.75	11.380%	$211.3436	$211.34	$211.35	$211.30
Purchase #6	$17.64	7.268%	$18.9221	$18.92	$18.90	$18.90
Purchase #7	$59.71	7.409%	$64.1339	$64.13	$64.15	$64.10
7 purchase totals =	$831.89		$909.6437	$909.63	$909.60	$909.50