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	$133.32	10.695%	$147.5786	$147.58	$147.60	$147.60
Purchase #2	$185.94	6.724%	$198.4426	$198.44	$198.45	$198.40
Purchase #3	$144.80	7.359%	$155.4558	$155.46	$155.45	$155.50
Purchase #4	$164.41	3.707%	$170.5047	$170.50	$170.50	$170.50
Purchase #5	$103.81	8.682%	$112.8228	$112.82	$112.80	$112.80
Purchase #6	$163.45	11.668%	$182.5213	$182.52	$182.50	$182.50
Purchase #7	$96.76	12.874%	$109.2169	$109.22	$109.20	$109.20
7 purchase totals =	$992.49		$1,076.5427	$1,076.54	$1,076.50	$1,076.50