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	$206.92	7.660%	$222.7701	$222.77	$222.75	$222.80
Purchase #2	$178.50	6.743%	$190.5363	$190.54	$190.55	$190.50
Purchase #3	$179.98	5.509%	$189.8951	$189.90	$189.90	$189.90
Purchase #4	$19.96	3.768%	$20.7121	$20.71	$20.70	$20.70
Purchase #5	$246.73	7.112%	$264.2774	$264.28	$264.30	$264.30
Purchase #6	$123.85	13.684%	$140.7976	$140.80	$140.80	$140.80
Purchase #7	$142.29	7.860%	$153.474	$153.47	$153.45	$153.50
7 purchase totals =	$1,098.23		$1,182.4626	$1,182.47	$1,182.45	$1,182.50