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	$88.49	13.503%	$100.4388	$100.44	$100.45	$100.40
Purchase #2	$153.88	12.260%	$172.7457	$172.75	$172.75	$172.70
Purchase #3	$178.32	10.190%	$196.4908	$196.49	$196.50	$196.50
Purchase #4	$205.88	3.649%	$213.3926	$213.39	$213.40	$213.40
Purchase #5	$113.73	7.708%	$122.4963	$122.50	$122.50	$122.50
Purchase #6	$147.81	13.687%	$168.0408	$168.04	$168.05	$168.00
Purchase #7	$220.82	10.237%	$243.4253	$243.43	$243.45	$243.40
7 purchase totals =	$1,108.93		$1,217.0303	$1,217.04	$1,217.10	$1,216.90