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	$157.80	11.269%	$175.5825	$175.58	$175.60	$175.60
Purchase #2	$69.31	5.147%	$72.8774	$72.88	$72.90	$72.90
Purchase #3	$6.90	13.452%	$7.8282	$7.83	$7.85	$7.80
Purchase #4	$37.85	12.556%	$42.6024	$42.60	$42.60	$42.60
Purchase #5	$102.93	3.574%	$106.6087	$106.61	$106.60	$106.60
Purchase #6	$100.34	7.282%	$107.6468	$107.65	$107.65	$107.60
Purchase #7	$33.97	11.777%	$37.9706	$37.97	$37.95	$38.00
7 purchase totals =	$509.10		$551.1166	$551.12	$551.15	$551.10