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	$112.44	3.623%	$116.5137	$116.51	$116.50	$116.50
Purchase #2	$149.39	11.513%	$166.5893	$166.59	$166.60	$166.60
Purchase #3	$62.61	5.822%	$66.2552	$66.26	$66.25	$66.30
Purchase #4	$74.60	9.489%	$81.6788	$81.68	$81.70	$81.70
Purchase #5	$225.58	13.831%	$256.78	$256.78	$256.80	$256.80
Purchase #6	$66.31	8.470%	$71.9265	$71.93	$71.95	$71.90
Purchase #7	$224.65	10.734%	$248.7639	$248.76	$248.75	$248.80
7 purchase totals =	$915.58		$1,008.5074	$1,008.51	$1,008.55	$1,008.60