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	$182.60	3.384%	$188.7792	$188.78	$188.80	$188.80
Purchase #2	$172.86	5.102%	$181.6793	$181.68	$181.70	$181.70
Purchase #3	$139.84	9.327%	$152.8829	$152.88	$152.90	$152.90
Purchase #4	$216.42	13.131%	$244.8381	$244.84	$244.85	$244.80
Purchase #5	$150.94	9.262%	$164.9201	$164.92	$164.90	$164.90
Purchase #6	$171.66	7.798%	$185.046	$185.05	$185.05	$185.00
Purchase #7	$192.39	3.386%	$198.9043	$198.90	$198.90	$198.90
7 purchase totals =	$1,226.71		$1,317.0499	$1,317.05	$1,317.10	$1,317.00