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	$209.32	13.726%	$238.0513	$238.05	$238.05	$238.10
Purchase #2	$162.74	11.803%	$181.9482	$181.95	$181.95	$181.90
Purchase #3	$162.29	11.182%	$180.4373	$180.44	$180.45	$180.40
Purchase #4	$70.82	11.305%	$78.8262	$78.83	$78.85	$78.80
Purchase #5	$40.98	8.456%	$44.4453	$44.45	$44.45	$44.40
Purchase #6	$146.56	3.431%	$151.5885	$151.59	$151.60	$151.60
Purchase #7	$206.91	13.117%	$234.0504	$234.05	$234.05	$234.10
7 purchase totals =	$999.62		$1,109.3472	$1,109.36	$1,109.40	$1,109.30