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	$49.36	10.764%	$54.6731	$54.67	$54.65	$54.70
Purchase #2	$11.36	8.790%	$12.3585	$12.36	$12.35	$12.40
Purchase #3	$31.58	12.706%	$35.5926	$35.59	$35.60	$35.60
Purchase #4	$137.27	11.597%	$153.1892	$153.19	$153.20	$153.20
Purchase #5	$48.77	10.353%	$53.8192	$53.82	$53.80	$53.80
Purchase #6	$104.44	4.786%	$109.4385	$109.44	$109.45	$109.40
Purchase #7	$222.69	7.226%	$238.7816	$238.78	$238.80	$238.80
7 purchase totals =	$605.47		$657.8527	$657.85	$657.85	$657.90