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	$193.76	12.743%	$218.4508	$218.45	$218.45	$218.50
Purchase #2	$94.68	12.416%	$106.4355	$106.44	$106.45	$106.40
Purchase #3	$161.85	6.244%	$171.9559	$171.96	$171.95	$172.00
Purchase #4	$16.68	7.203%	$17.8815	$17.88	$17.90	$17.90
Purchase #5	$228.32	4.304%	$238.1469	$238.15	$238.15	$238.10
Purchase #6	$53.77	12.559%	$60.523	$60.52	$60.50	$60.50
Purchase #7	$159.34	3.446%	$164.8309	$164.83	$164.85	$164.80
7 purchase totals =	$908.40		$978.2245	$978.23	$978.25	$978.20