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	$102.65	13.334%	$116.3374	$116.34	$116.35	$116.30
Purchase #2	$143.25	13.163%	$162.106	$162.11	$162.10	$162.10
Purchase #3	$154.74	4.718%	$162.0406	$162.04	$162.05	$162.00
Purchase #4	$118.38	7.303%	$127.0253	$127.03	$127.05	$127.00
Purchase #5	$35.68	5.272%	$37.561	$37.56	$37.55	$37.60
Purchase #6	$156.66	8.596%	$170.1265	$170.13	$170.15	$170.10
Purchase #7	$52.82	10.752%	$58.4992	$58.50	$58.50	$58.50
7 purchase totals =	$764.18		$833.6960	$833.71	$833.75	$833.60