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	$72.52	7.113%	$77.6783	$77.68	$77.70	$77.70
Purchase #2	$212.78	6.730%	$227.1001	$227.10	$227.10	$227.10
Purchase #3	$238.64	3.651%	$247.3527	$247.35	$247.35	$247.40
Purchase #4	$69.83	4.139%	$72.7203	$72.72	$72.70	$72.70
Purchase #5	$92.25	6.759%	$98.4852	$98.49	$98.50	$98.50
Purchase #6	$19.30	13.491%	$21.9038	$21.90	$21.90	$21.90
Purchase #7	$102.43	13.531%	$116.2898	$116.29	$116.30	$116.30
7 purchase totals =	$807.75		$861.5302	$861.53	$861.55	$861.60