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	$70.34	9.435%	$76.9766	$76.98	$77.00	$77.00
Purchase #2	$17.59	6.346%	$18.7063	$18.71	$18.70	$18.70
Purchase #3	$228.98	13.320%	$259.4801	$259.48	$259.50	$259.50
Purchase #4	$128.31	8.578%	$139.3164	$139.32	$139.30	$139.30
Purchase #5	$22.99	12.733%	$25.9173	$25.92	$25.90	$25.90
Purchase #6	$98.37	11.316%	$109.5015	$109.50	$109.50	$109.50
Purchase #7	$92.38	4.423%	$96.466	$96.47	$96.45	$96.50
7 purchase totals =	$658.96		$726.3642	$726.38	$726.35	$726.40