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	$33.29	6.791%	$35.5507	$35.55	$35.55	$35.60
Purchase #2	$169.79	8.603%	$184.397	$184.40	$184.40	$184.40
Purchase #3	$14.85	11.849%	$16.6096	$16.61	$16.60	$16.60
Purchase #4	$72.95	7.712%	$78.5759	$78.58	$78.60	$78.60
Purchase #5	$56.83	13.655%	$64.5901	$64.59	$64.60	$64.60
Purchase #6	$45.38	9.193%	$49.5518	$49.55	$49.55	$49.60
Purchase #7	$9.50	6.784%	$10.1445	$10.14	$10.15	$10.10
7 purchase totals =	$402.59		$439.4196	$439.42	$439.45	$439.50