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	$168.64	13.566%	$191.5177	$191.52	$191.50	$191.50
Purchase #2	$32.76	7.270%	$35.1417	$35.14	$35.15	$35.10
Purchase #3	$149.82	5.741%	$158.4212	$158.42	$158.40	$158.40
Purchase #4	$153.47	5.447%	$161.8295	$161.83	$161.85	$161.80
Purchase #5	$52.55	9.332%	$57.454	$57.45	$57.45	$57.50
Purchase #6	$90.75	10.135%	$99.9475	$99.95	$99.95	$99.90
Purchase #7	$173.34	6.687%	$184.9312	$184.93	$184.95	$184.90
7 purchase totals =	$821.33		$889.2428	$889.24	$889.25	$889.10