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	$197.49	5.476%	$208.3046	$208.30	$208.30	$208.30
Purchase #2	$157.53	7.535%	$169.3999	$169.40	$169.40	$169.40
Purchase #3	$35.25	10.161%	$38.8318	$38.83	$38.85	$38.80
Purchase #4	$53.60	5.260%	$56.4194	$56.42	$56.40	$56.40
Purchase #5	$65.52	9.671%	$71.8564	$71.86	$71.85	$71.90
Purchase #6	$154.69	7.131%	$165.7209	$165.72	$165.70	$165.70
Purchase #7	$218.48	13.755%	$248.5319	$248.53	$248.55	$248.50
7 purchase totals =	$882.56		$959.0649	$959.06	$959.05	$959.00