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	$82.72	3.494%	$85.6102	$85.61	$85.60	$85.60
Purchase #2	$56.92	4.132%	$59.2719	$59.27	$59.25	$59.30
Purchase #3	$221.39	11.539%	$246.9362	$246.94	$246.95	$246.90
Purchase #4	$158.78	12.709%	$178.9594	$178.96	$178.95	$179.00
Purchase #5	$168.72	4.806%	$176.8287	$176.83	$176.85	$176.80
Purchase #6	$79.85	3.784%	$82.8715	$82.87	$82.85	$82.90
Purchase #7	$5.38	5.249%	$5.6624	$5.66	$5.65	$5.70
7 purchase totals =	$773.76		$836.1403	$836.14	$836.10	$836.20