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	$145.61	4.295%	$151.8639	$151.86	$151.85	$151.90
Purchase #2	$59.82	9.579%	$65.5502	$65.55	$65.55	$65.60
Purchase #3	$137.92	5.200%	$145.0918	$145.09	$145.10	$145.10
Purchase #4	$71.38	5.850%	$75.5557	$75.56	$75.55	$75.60
Purchase #5	$11.59	4.758%	$12.1415	$12.14	$12.15	$12.10
Purchase #6	$92.60	11.784%	$103.512	$103.51	$103.50	$103.50
Purchase #7	$171.27	5.213%	$180.1983	$180.20	$180.20	$180.20
7 purchase totals =	$690.19		$733.9134	$733.91	$733.90	$734.00