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	$100.89	4.612%	$105.543	$105.54	$105.55	$105.50
Purchase #2	$85.39	5.315%	$89.9285	$89.93	$89.95	$89.90
Purchase #3	$52.32	12.142%	$58.6727	$58.67	$58.65	$58.70
Purchase #4	$120.97	11.485%	$134.8634	$134.86	$134.85	$134.90
Purchase #5	$46.96	9.634%	$51.4841	$51.48	$51.50	$51.50
Purchase #6	$108.32	11.141%	$120.3879	$120.39	$120.40	$120.40
Purchase #7	$13.27	11.346%	$14.7756	$14.78	$14.80	$14.80
7 purchase totals =	$528.12		$575.6552	$575.65	$575.70	$575.70