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	$145.41	3.729%	$150.8323	$150.83	$150.85	$150.80
Purchase #2	$139.73	5.735%	$147.7435	$147.74	$147.75	$147.70
Purchase #3	$187.96	11.119%	$208.8593	$208.86	$208.85	$208.90
Purchase #4	$224.44	6.401%	$238.8064	$238.81	$238.80	$238.80
Purchase #5	$91.60	10.257%	$100.9954	$101.00	$101.00	$101.00
Purchase #6	$20.86	5.707%	$22.0505	$22.05	$22.05	$22.10
Purchase #7	$89.46	9.693%	$98.1314	$98.13	$98.15	$98.10
7 purchase totals =	$899.46		$967.4188	$967.42	$967.45	$967.40