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	$101.92	7.556%	$109.6211	$109.62	$109.60	$109.60
Purchase #2	$133.66	6.658%	$142.5591	$142.56	$142.55	$142.60
Purchase #3	$54.98	5.213%	$57.8461	$57.85	$57.85	$57.80
Purchase #4	$154.69	7.333%	$166.0334	$166.03	$166.05	$166.00
Purchase #5	$218.50	10.191%	$240.7673	$240.77	$240.75	$240.80
Purchase #6	$218.91	4.684%	$229.1637	$229.16	$229.15	$229.20
Purchase #7	$118.38	7.516%	$127.2774	$127.28	$127.30	$127.30
7 purchase totals =	$1,001.04		$1,073.2681	$1,073.27	$1,073.25	$1,073.30