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	$46.64	9.567%	$51.102	$51.10	$51.10	$51.10
Purchase #2	$151.31	8.429%	$164.0639	$164.06	$164.05	$164.10
Purchase #3	$140.59	10.480%	$155.3238	$155.32	$155.30	$155.30
Purchase #4	$158.48	6.416%	$168.6481	$168.65	$168.65	$168.60
Purchase #5	$221.77	5.211%	$233.3264	$233.33	$233.35	$233.30
Purchase #6	$74.56	7.577%	$80.2094	$80.21	$80.20	$80.20
Purchase #7	$89.81	11.328%	$99.9837	$99.98	$100.00	$100.00
7 purchase totals =	$883.16		$952.6573	$952.65	$952.65	$952.60