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	$92.88	10.263%	$102.4123	$102.41	$102.40	$102.40
Purchase #2	$139.75	4.354%	$145.8347	$145.83	$145.85	$145.80
Purchase #3	$215.43	8.259%	$233.2224	$233.22	$233.20	$233.20
Purchase #4	$57.48	6.761%	$61.3662	$61.37	$61.35	$61.40
Purchase #5	$92.77	3.343%	$95.8713	$95.87	$95.85	$95.90
Purchase #6	$11.48	11.177%	$12.7631	$12.76	$12.75	$12.80
Purchase #7	$144.38	12.245%	$162.0593	$162.06	$162.05	$162.10
7 purchase totals =	$754.17		$813.5293	$813.52	$813.45	$813.60