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	$247.28	6.348%	$262.9773	$262.98	$263.00	$263.00
Purchase #2	$154.79	10.648%	$171.272	$171.27	$171.25	$171.30
Purchase #3	$210.83	3.148%	$217.4669	$217.47	$217.45	$217.50
Purchase #4	$43.66	8.826%	$47.5134	$47.51	$47.50	$47.50
Purchase #5	$180.89	13.773%	$205.804	$205.80	$205.80	$205.80
Purchase #6	$11.54	7.145%	$12.3645	$12.36	$12.35	$12.40
Purchase #7	$57.77	5.512%	$60.9543	$60.95	$60.95	$61.00
7 purchase totals =	$906.76		$978.3524	$978.34	$978.30	$978.50