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	$188.71	11.822%	$211.0193	$211.02	$211.00	$211.00
Purchase #2	$242.82	9.569%	$266.0554	$266.06	$266.05	$266.10
Purchase #3	$150.69	11.829%	$168.5151	$168.52	$168.50	$168.50
Purchase #4	$93.96	5.220%	$98.8647	$98.86	$98.85	$98.90
Purchase #5	$19.30	9.773%	$21.1862	$21.19	$21.20	$21.20
Purchase #6	$76.70	4.792%	$80.3755	$80.38	$80.40	$80.40
Purchase #7	$186.88	13.105%	$211.3706	$211.37	$211.35	$211.40
7 purchase totals =	$959.06		$1,057.3868	$1,057.40	$1,057.35	$1,057.50