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	$194.30	7.112%	$208.1186	$208.12	$208.10	$208.10
Purchase #2	$126.93	3.864%	$131.8346	$131.83	$131.85	$131.80
Purchase #3	$50.27	11.827%	$56.2154	$56.22	$56.20	$56.20
Purchase #4	$205.82	7.286%	$220.816	$220.82	$220.80	$220.80
Purchase #5	$85.72	7.823%	$92.4259	$92.43	$92.45	$92.40
Purchase #6	$83.27	7.416%	$89.4453	$89.45	$89.45	$89.40
Purchase #7	$166.65	10.324%	$183.8549	$183.85	$183.85	$183.90
7 purchase totals =	$912.96		$982.7107	$982.72	$982.70	$982.60