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	$113.72	11.200%	$126.4566	$126.46	$126.45	$126.50
Purchase #2	$96.45	3.212%	$99.548	$99.55	$99.55	$99.50
Purchase #3	$89.56	11.872%	$100.1926	$100.19	$100.20	$100.20
Purchase #4	$181.53	5.435%	$191.3962	$191.40	$191.40	$191.40
Purchase #5	$215.60	9.456%	$235.9871	$235.99	$236.00	$236.00
Purchase #6	$41.89	8.226%	$45.3359	$45.34	$45.35	$45.30
Purchase #7	$94.85	4.846%	$99.4464	$99.45	$99.45	$99.40
7 purchase totals =	$833.60		$898.3628	$898.38	$898.40	$898.30