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	$46.97	11.230%	$52.2447	$52.24	$52.25	$52.20
Purchase #2	$64.37	4.710%	$67.4018	$67.40	$67.40	$67.40
Purchase #3	$172.53	5.296%	$181.6672	$181.67	$181.65	$181.70
Purchase #4	$183.91	7.262%	$197.2655	$197.27	$197.25	$197.30
Purchase #5	$32.74	13.509%	$37.1628	$37.16	$37.15	$37.20
Purchase #6	$109.54	13.115%	$123.9062	$123.91	$123.90	$123.90
Purchase #7	$139.80	9.144%	$152.5833	$152.58	$152.60	$152.60
7 purchase totals =	$749.86		$812.2315	$812.23	$812.20	$812.30