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	$210.87	3.148%	$217.5082	$217.51	$217.50	$217.50
Purchase #2	$193.74	6.238%	$205.8255	$205.83	$205.85	$205.80
Purchase #3	$134.37	5.497%	$141.7563	$141.76	$141.75	$141.80
Purchase #4	$164.58	10.499%	$181.8593	$181.86	$181.85	$181.90
Purchase #5	$54.32	10.256%	$59.8911	$59.89	$59.90	$59.90
Purchase #6	$250.83	10.629%	$277.4907	$277.49	$277.50	$277.50
Purchase #7	$226.52	13.176%	$256.3663	$256.37	$256.35	$256.40
7 purchase totals =	$1,235.23		$1,340.6974	$1,340.71	$1,340.70	$1,340.80