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	$74.85	3.429%	$77.4166	$77.42	$77.40	$77.40
Purchase #2	$118.50	5.784%	$125.354	$125.35	$125.35	$125.40
Purchase #3	$69.51	11.565%	$77.5488	$77.55	$77.55	$77.50
Purchase #4	$90.30	9.874%	$99.2162	$99.22	$99.20	$99.20
Purchase #5	$48.33	10.659%	$53.4815	$53.48	$53.50	$53.50
Purchase #6	$50.28	4.257%	$52.4204	$52.42	$52.40	$52.40
Purchase #7	$214.98	3.231%	$221.926	$221.93	$221.95	$221.90
7 purchase totals =	$666.75		$707.3635	$707.37	$707.35	$707.30