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	$239.35	4.137%	$249.2519	$249.25	$249.25	$249.30
Purchase #2	$86.70	10.468%	$95.7758	$95.78	$95.80	$95.80
Purchase #3	$231.31	6.278%	$245.8316	$245.83	$245.85	$245.80
Purchase #4	$104.85	6.805%	$111.985	$111.99	$112.00	$112.00
Purchase #5	$50.88	7.154%	$54.52	$54.52	$54.50	$54.50
Purchase #6	$152.93	13.464%	$173.5205	$173.52	$173.50	$173.50
Purchase #7	$61.27	3.429%	$63.3709	$63.37	$63.35	$63.40
7 purchase totals =	$927.29		$994.2557	$994.26	$994.25	$994.30