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	$100.55	3.197%	$103.7646	$103.76	$103.75	$103.80
Purchase #2	$181.26	12.823%	$204.503	$204.50	$204.50	$204.50
Purchase #3	$104.80	13.404%	$118.8474	$118.85	$118.85	$118.80
Purchase #4	$239.66	9.253%	$261.8357	$261.84	$261.85	$261.80
Purchase #5	$85.56	8.375%	$92.7257	$92.73	$92.75	$92.70
Purchase #6	$198.99	7.162%	$213.2417	$213.24	$213.25	$213.20
Purchase #7	$59.89	11.584%	$66.8277	$66.83	$66.85	$66.80
7 purchase totals =	$970.71		$1,061.7458	$1,061.75	$1,061.80	$1,061.60