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	$129.51	11.191%	$144.0035	$144.00	$144.00	$144.00
Purchase #2	$123.33	4.272%	$128.5987	$128.60	$128.60	$128.60
Purchase #3	$56.51	12.501%	$63.5743	$63.57	$63.55	$63.60
Purchase #4	$248.50	5.775%	$262.8509	$262.85	$262.85	$262.90
Purchase #5	$148.72	9.327%	$162.5911	$162.59	$162.60	$162.60
Purchase #6	$134.44	6.842%	$143.6384	$143.64	$143.65	$143.60
Purchase #7	$174.69	10.417%	$192.8875	$192.89	$192.90	$192.90
7 purchase totals =	$1,015.70		$1,098.1444	$1,098.14	$1,098.15	$1,098.20