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	$117.42	11.595%	$131.0348	$131.03	$131.05	$131.00
Purchase #2	$133.63	9.677%	$146.5614	$146.56	$146.55	$146.60
Purchase #3	$190.43	5.118%	$200.1762	$200.18	$200.20	$200.20
Purchase #4	$241.88	8.528%	$262.5075	$262.51	$262.50	$262.50
Purchase #5	$34.35	9.526%	$37.6222	$37.62	$37.60	$37.60
Purchase #6	$174.86	6.213%	$185.7241	$185.72	$185.70	$185.70
Purchase #7	$153.57	7.202%	$164.6301	$164.63	$164.65	$164.60
7 purchase totals =	$1,046.14		$1,128.2563	$1,128.25	$1,128.25	$1,128.20