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	$60.38	6.117%	$64.0734	$64.07	$64.05	$64.10
Purchase #2	$65.37	11.525%	$72.9039	$72.90	$72.90	$72.90
Purchase #3	$142.69	7.253%	$153.0393	$153.04	$153.05	$153.00
Purchase #4	$54.66	4.594%	$57.1711	$57.17	$57.15	$57.20
Purchase #5	$152.27	10.125%	$167.6873	$167.69	$167.70	$167.70
Purchase #6	$65.42	7.699%	$70.4567	$70.46	$70.45	$70.50
Purchase #7	$233.50	3.602%	$241.9107	$241.91	$241.90	$241.90
7 purchase totals =	$774.29		$827.2424	$827.24	$827.20	$827.30