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	$108.52	8.762%	$118.0285	$118.03	$118.05	$118.00
Purchase #2	$66.30	8.819%	$72.147	$72.15	$72.15	$72.10
Purchase #3	$213.61	11.729%	$238.6643	$238.66	$238.65	$238.70
Purchase #4	$178.68	12.123%	$200.3414	$200.34	$200.35	$200.30
Purchase #5	$107.68	6.558%	$114.7417	$114.74	$114.75	$114.70
Purchase #6	$79.28	8.692%	$86.171	$86.17	$86.15	$86.20
Purchase #7	$226.60	13.300%	$256.7378	$256.74	$256.75	$256.70
7 purchase totals =	$980.67		$1,086.8317	$1,086.83	$1,086.85	$1,086.70