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	$138.33	9.104%	$150.9236	$150.92	$150.90	$150.90
Purchase #2	$13.56	4.311%	$14.1446	$14.14	$14.15	$14.10
Purchase #3	$134.54	13.655%	$152.9114	$152.91	$152.90	$152.90
Purchase #4	$66.39	3.691%	$68.8405	$68.84	$68.85	$68.80
Purchase #5	$205.56	12.776%	$231.8223	$231.82	$231.80	$231.80
Purchase #6	$170.34	6.197%	$180.896	$180.90	$180.90	$180.90
Purchase #7	$139.87	9.443%	$153.0779	$153.08	$153.10	$153.10
7 purchase totals =	$868.59		$952.6163	$952.61	$952.60	$952.50