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	$99.40	5.186%	$104.5549	$104.55	$104.55	$104.60
Purchase #2	$81.40	11.683%	$90.91	$90.91	$90.90	$90.90
Purchase #3	$50.64	9.408%	$55.4042	$55.40	$55.40	$55.40
Purchase #4	$117.80	10.696%	$130.3999	$130.40	$130.40	$130.40
Purchase #5	$225.43	4.262%	$235.0378	$235.04	$235.05	$235.00
Purchase #6	$89.90	5.416%	$94.769	$94.77	$94.75	$94.80
Purchase #7	$68.43	5.629%	$72.2819	$72.28	$72.30	$72.30
7 purchase totals =	$733.00		$783.3577	$783.35	$783.35	$783.40