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	$100.60	5.172%	$105.803	$105.80	$105.80	$105.80
Purchase #2	$117.73	9.505%	$128.9202	$128.92	$128.90	$128.90
Purchase #3	$82.43	10.864%	$91.3852	$91.39	$91.40	$91.40
Purchase #4	$35.25	7.324%	$37.8317	$37.83	$37.85	$37.80
Purchase #5	$18.72	5.295%	$19.7112	$19.71	$19.70	$19.70
Purchase #6	$125.59	9.436%	$137.4407	$137.44	$137.45	$137.40
Purchase #7	$91.34	4.194%	$95.1708	$95.17	$95.15	$95.20
7 purchase totals =	$571.66		$616.2628	$616.26	$616.25	$616.20