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	$153.28	6.289%	$162.9198	$162.92	$162.90	$162.90
Purchase #2	$205.58	6.712%	$219.3785	$219.38	$219.40	$219.40
Purchase #3	$28.85	3.534%	$29.8696	$29.87	$29.85	$29.90
Purchase #4	$70.30	4.506%	$73.4677	$73.47	$73.45	$73.50
Purchase #5	$211.74	9.501%	$231.8574	$231.86	$231.85	$231.90
Purchase #6	$86.66	4.831%	$90.8465	$90.85	$90.85	$90.80
Purchase #7	$50.29	5.389%	$53.0001	$53.00	$53.00	$53.00
7 purchase totals =	$806.70		$861.3396	$861.35	$861.30	$861.40