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	$94.40	9.633%	$103.4936	$103.49	$103.50	$103.50
Purchase #2	$140.81	12.799%	$158.8323	$158.83	$158.85	$158.80
Purchase #3	$203.47	10.233%	$224.2911	$224.29	$224.30	$224.30
Purchase #4	$35.35	7.304%	$37.932	$37.93	$37.95	$37.90
Purchase #5	$238.70	13.836%	$271.7265	$271.73	$271.75	$271.70
Purchase #6	$250.76	10.772%	$277.7719	$277.77	$277.75	$277.80
Purchase #7	$153.92	4.260%	$160.477	$160.48	$160.50	$160.50
7 purchase totals =	$1,117.41		$1,234.5244	$1,234.52	$1,234.60	$1,234.50