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	$245.49	11.264%	$273.142	$273.14	$273.15	$273.10
Purchase #2	$96.41	5.658%	$101.8649	$101.86	$101.85	$101.90
Purchase #3	$158.35	9.630%	$173.5991	$173.60	$173.60	$173.60
Purchase #4	$120.79	13.756%	$137.4059	$137.41	$137.40	$137.40
Purchase #5	$227.46	4.763%	$238.2939	$238.29	$238.30	$238.30
Purchase #6	$227.41	7.390%	$244.2156	$244.22	$244.20	$244.20
Purchase #7	$55.76	3.154%	$57.5187	$57.52	$57.50	$57.50
7 purchase totals =	$1,131.67		$1,226.0401	$1,226.04	$1,226.00	$1,226.00