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	$77.58	4.806%	$81.3085	$81.31	$81.30	$81.30
Purchase #2	$244.32	10.816%	$270.7457	$270.75	$270.75	$270.70
Purchase #3	$113.52	8.800%	$123.5098	$123.51	$123.50	$123.50
Purchase #4	$180.83	4.283%	$188.5749	$188.57	$188.55	$188.60
Purchase #5	$63.28	5.452%	$66.73	$66.73	$66.75	$66.70
Purchase #6	$247.42	7.626%	$266.2882	$266.29	$266.30	$266.30
Purchase #7	$139.55	4.249%	$145.4795	$145.48	$145.50	$145.50
7 purchase totals =	$1,066.50		$1,142.6366	$1,142.64	$1,142.65	$1,142.60