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	$52.46	8.217%	$56.7706	$56.77	$56.75	$56.80
Purchase #2	$105.32	5.181%	$110.7766	$110.78	$110.80	$110.80
Purchase #3	$20.74	5.694%	$21.9209	$21.92	$21.90	$21.90
Purchase #4	$102.71	5.540%	$108.4001	$108.40	$108.40	$108.40
Purchase #5	$247.78	4.864%	$259.832	$259.83	$259.85	$259.80
Purchase #6	$57.78	8.503%	$62.693	$62.69	$62.70	$62.70
Purchase #7	$144.46	11.330%	$160.8273	$160.83	$160.85	$160.80
7 purchase totals =	$731.25		$781.2205	$781.22	$781.25	$781.20