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	$209.63	11.195%	$233.0981	$233.10	$233.10	$233.10
Purchase #2	$250.60	9.487%	$274.3744	$274.37	$274.35	$274.40
Purchase #3	$55.47	5.488%	$58.5142	$58.51	$58.50	$58.50
Purchase #4	$37.50	11.553%	$41.8324	$41.83	$41.85	$41.80
Purchase #5	$42.96	5.393%	$45.2768	$45.28	$45.30	$45.30
Purchase #6	$52.41	13.307%	$59.3842	$59.38	$59.40	$59.40
Purchase #7	$12.98	10.314%	$14.3188	$14.32	$14.30	$14.30
7 purchase totals =	$661.55		$726.7989	$726.79	$726.80	$726.80