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	$142.99	3.105%	$147.4298	$147.43	$147.45	$147.40
Purchase #2	$76.34	11.847%	$85.384	$85.38	$85.40	$85.40
Purchase #3	$48.30	11.487%	$53.8482	$53.85	$53.85	$53.80
Purchase #4	$97.62	13.770%	$111.0623	$111.06	$111.05	$111.10
Purchase #5	$17.34	5.761%	$18.339	$18.34	$18.35	$18.30
Purchase #6	$93.36	13.831%	$106.2726	$106.27	$106.25	$106.30
Purchase #7	$156.35	10.689%	$173.0623	$173.06	$173.05	$173.10
7 purchase totals =	$632.30		$695.3982	$695.39	$695.40	$695.40