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	$104.38	13.600%	$118.5757	$118.58	$118.60	$118.60
Purchase #2	$188.47	10.847%	$208.9133	$208.91	$208.90	$208.90
Purchase #3	$135.38	4.822%	$141.908	$141.91	$141.90	$141.90
Purchase #4	$212.61	4.459%	$222.0903	$222.09	$222.10	$222.10
Purchase #5	$66.28	9.459%	$72.5494	$72.55	$72.55	$72.50
Purchase #6	$55.83	4.780%	$58.4987	$58.50	$58.50	$58.50
Purchase #7	$244.53	11.247%	$272.0323	$272.03	$272.05	$272.00
7 purchase totals =	$1,007.48		$1,094.5677	$1,094.57	$1,094.60	$1,094.50