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	$111.36	7.388%	$119.5873	$119.59	$119.60	$119.60
Purchase #2	$147.53	4.254%	$153.8059	$153.81	$153.80	$153.80
Purchase #3	$239.57	10.727%	$265.2687	$265.27	$265.25	$265.30
Purchase #4	$58.56	8.570%	$63.5786	$63.58	$63.60	$63.60
Purchase #5	$43.55	4.506%	$45.5124	$45.51	$45.50	$45.50
Purchase #6	$76.92	12.734%	$86.715	$86.72	$86.70	$86.70
Purchase #7	$12.91	7.743%	$13.9096	$13.91	$13.90	$13.90
7 purchase totals =	$690.40		$748.3775	$748.39	$748.35	$748.40