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	$144.46	13.761%	$164.3391	$164.34	$164.35	$164.30
Purchase #2	$187.71	4.572%	$196.2921	$196.29	$196.30	$196.30
Purchase #3	$145.31	8.195%	$157.2182	$157.22	$157.20	$157.20
Purchase #4	$147.30	9.209%	$160.8649	$160.86	$160.85	$160.90
Purchase #5	$241.58	10.352%	$266.5884	$266.59	$266.60	$266.60
Purchase #6	$58.98	7.855%	$63.6129	$63.61	$63.60	$63.60
Purchase #7	$60.77	10.810%	$67.3392	$67.34	$67.35	$67.30
7 purchase totals =	$986.11		$1,076.2548	$1,076.25	$1,076.25	$1,076.20