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	$77.95	7.581%	$83.8594	$83.86	$83.85	$83.90
Purchase #2	$246.58	5.295%	$259.6364	$259.64	$259.65	$259.60
Purchase #3	$132.29	3.755%	$137.2575	$137.26	$137.25	$137.30
Purchase #4	$208.94	6.469%	$222.4563	$222.46	$222.45	$222.50
Purchase #5	$145.91	5.656%	$154.1627	$154.16	$154.15	$154.20
Purchase #6	$82.42	9.127%	$89.9425	$89.94	$89.95	$89.90
Purchase #7	$197.58	10.292%	$217.9149	$217.91	$217.90	$217.90
7 purchase totals =	$1,091.67		$1,165.2297	$1,165.23	$1,165.20	$1,165.30