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	$91.64	10.777%	$101.516	$101.52	$101.50	$101.50
Purchase #2	$71.33	8.652%	$77.5015	$77.50	$77.50	$77.50
Purchase #3	$165.51	8.395%	$179.4046	$179.40	$179.40	$179.40
Purchase #4	$129.42	13.241%	$146.5565	$146.56	$146.55	$146.60
Purchase #5	$183.34	13.739%	$208.5291	$208.53	$208.55	$208.50
Purchase #6	$217.84	10.389%	$240.4714	$240.47	$240.45	$240.50
Purchase #7	$60.76	5.114%	$63.8673	$63.87	$63.85	$63.90
7 purchase totals =	$919.84		$1,017.8464	$1,017.85	$1,017.80	$1,017.90