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	$122.64	7.198%	$131.4676	$131.47	$131.45	$131.50
Purchase #2	$59.40	13.797%	$67.5954	$67.60	$67.60	$67.60
Purchase #3	$178.64	5.568%	$188.5867	$188.59	$188.60	$188.60
Purchase #4	$8.49	11.543%	$9.47	$9.47	$9.45	$9.50
Purchase #5	$24.29	12.825%	$27.4052	$27.41	$27.40	$27.40
Purchase #6	$196.97	5.791%	$208.3765	$208.38	$208.40	$208.40
Purchase #7	$155.41	11.212%	$172.8346	$172.83	$172.85	$172.80
7 purchase totals =	$745.84		$805.7360	$805.75	$805.75	$805.80