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	$111.97	4.475%	$116.9807	$116.98	$117.00	$117.00
Purchase #2	$248.54	9.490%	$272.1264	$272.13	$272.15	$272.10
Purchase #3	$158.82	5.648%	$167.7902	$167.79	$167.80	$167.80
Purchase #4	$234.89	13.311%	$266.1562	$266.16	$266.15	$266.20
Purchase #5	$146.56	13.284%	$166.029	$166.03	$166.05	$166.00
Purchase #6	$146.86	6.825%	$156.8832	$156.88	$156.90	$156.90
Purchase #7	$227.61	8.315%	$246.5358	$246.54	$246.55	$246.50
7 purchase totals =	$1,275.25		$1,392.5015	$1,392.51	$1,392.60	$1,392.50