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	$55.43	13.836%	$63.0993	$63.10	$63.10	$63.10
Purchase #2	$35.92	5.416%	$37.8654	$37.87	$37.85	$37.90
Purchase #3	$41.79	6.389%	$44.46	$44.46	$44.45	$44.50
Purchase #4	$112.85	13.573%	$128.1671	$128.17	$128.15	$128.20
Purchase #5	$125.77	5.844%	$133.12	$133.12	$133.10	$133.10
Purchase #6	$27.46	4.103%	$28.5867	$28.59	$28.60	$28.60
Purchase #7	$52.25	9.219%	$57.0669	$57.07	$57.05	$57.10
7 purchase totals =	$451.47		$492.3654	$492.38	$492.30	$492.50