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	$69.48	12.627%	$78.2532	$78.25	$78.25	$78.30
Purchase #2	$235.32	8.462%	$255.2328	$255.23	$255.25	$255.20
Purchase #3	$249.93	11.757%	$279.3143	$279.31	$279.30	$279.30
Purchase #4	$229.90	9.811%	$252.4555	$252.46	$252.45	$252.50
Purchase #5	$38.89	6.417%	$41.3856	$41.39	$41.40	$41.40
Purchase #6	$155.81	4.469%	$162.7731	$162.77	$162.75	$162.80
Purchase #7	$92.46	4.562%	$96.678	$96.68	$96.70	$96.70
7 purchase totals =	$1,071.79		$1,166.0925	$1,166.09	$1,166.10	$1,166.20