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	$141.37	4.622%	$147.9041	$147.90	$147.90	$147.90
Purchase #2	$91.31	13.455%	$103.5958	$103.60	$103.60	$103.60
Purchase #3	$26.63	4.228%	$27.7559	$27.76	$27.75	$27.80
Purchase #4	$45.41	12.630%	$51.1453	$51.15	$51.15	$51.10
Purchase #5	$111.81	13.453%	$126.8518	$126.85	$126.85	$126.90
Purchase #6	$181.48	5.584%	$191.6138	$191.61	$191.60	$191.60
Purchase #7	$102.61	10.188%	$113.0639	$113.06	$113.05	$113.10
7 purchase totals =	$700.62		$761.9306	$761.93	$761.90	$762.00