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	$157.30	11.768%	$175.8111	$175.81	$175.80	$175.80
Purchase #2	$95.93	4.375%	$100.1269	$100.13	$100.15	$100.10
Purchase #3	$17.96	7.462%	$19.3002	$19.30	$19.30	$19.30
Purchase #4	$35.25	13.865%	$40.1374	$40.14	$40.15	$40.10
Purchase #5	$78.63	10.423%	$86.8256	$86.83	$86.85	$86.80
Purchase #6	$247.32	5.307%	$260.4453	$260.45	$260.45	$260.40
Purchase #7	$149.69	12.588%	$168.533	$168.53	$168.55	$168.50
7 purchase totals =	$782.08		$851.1795	$851.19	$851.25	$851.00