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	$162.78	12.439%	$183.0282	$183.03	$183.05	$183.00
Purchase #2	$144.37	7.186%	$154.7444	$154.74	$154.75	$154.70
Purchase #3	$242.29	5.817%	$256.384	$256.38	$256.40	$256.40
Purchase #4	$89.92	11.768%	$100.5018	$100.50	$100.50	$100.50
Purchase #5	$66.48	7.178%	$71.2519	$71.25	$71.25	$71.30
Purchase #6	$27.89	12.169%	$31.2839	$31.28	$31.30	$31.30
Purchase #7	$220.87	10.553%	$244.1784	$244.18	$244.20	$244.20
7 purchase totals =	$954.60		$1,041.3726	$1,041.36	$1,041.45	$1,041.40