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	$26.31	12.358%	$29.5614	$29.56	$29.55	$29.60
Purchase #2	$224.60	13.866%	$255.743	$255.74	$255.75	$255.70
Purchase #3	$123.81	4.581%	$129.4817	$129.48	$129.50	$129.50
Purchase #4	$152.30	3.141%	$157.0837	$157.08	$157.10	$157.10
Purchase #5	$92.81	7.570%	$99.8357	$99.84	$99.85	$99.80
Purchase #6	$228.67	13.674%	$259.9383	$259.94	$259.95	$259.90
Purchase #7	$153.64	12.279%	$172.5055	$172.51	$172.50	$172.50
7 purchase totals =	$1,002.14		$1,104.1493	$1,104.15	$1,104.20	$1,104.10