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	$102.61	10.269%	$113.147	$113.15	$113.15	$113.10
Purchase #2	$172.77	10.316%	$190.593	$190.59	$190.60	$190.60
Purchase #3	$99.88	3.580%	$103.4557	$103.46	$103.45	$103.50
Purchase #4	$189.75	10.788%	$210.2202	$210.22	$210.20	$210.20
Purchase #5	$27.42	3.260%	$28.3139	$28.31	$28.30	$28.30
Purchase #6	$15.85	3.416%	$16.3914	$16.39	$16.40	$16.40
Purchase #7	$25.39	8.316%	$27.5014	$27.50	$27.50	$27.50
7 purchase totals =	$633.67		$689.6226	$689.62	$689.60	$689.60