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	$20.89	4.699%	$21.8716	$21.87	$21.85	$21.90
Purchase #2	$32.75	7.440%	$35.1866	$35.19	$35.20	$35.20
Purchase #3	$160.40	3.283%	$165.6659	$165.67	$165.65	$165.70
Purchase #4	$140.92	6.537%	$150.1319	$150.13	$150.15	$150.10
Purchase #5	$61.75	5.693%	$65.2654	$65.27	$65.25	$65.30
Purchase #6	$10.97	3.207%	$11.3218	$11.32	$11.30	$11.30
Purchase #7	$216.56	5.253%	$227.9359	$227.94	$227.95	$227.90
7 purchase totals =	$644.24		$677.3791	$677.39	$677.35	$677.40