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	$128.62	4.341%	$134.2034	$134.20	$134.20	$134.20
Purchase #2	$81.26	8.669%	$88.3044	$88.30	$88.30	$88.30
Purchase #3	$88.94	12.623%	$100.1669	$100.17	$100.15	$100.20
Purchase #4	$105.75	5.464%	$111.5282	$111.53	$111.55	$111.50
Purchase #5	$56.67	9.150%	$61.8553	$61.86	$61.85	$61.90
Purchase #6	$246.26	13.428%	$279.3278	$279.33	$279.35	$279.30
Purchase #7	$229.86	3.796%	$238.5855	$238.59	$238.60	$238.60
7 purchase totals =	$937.36		$1,013.9715	$1,013.98	$1,014.00	$1,014.00