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	$164.51	3.229%	$169.822	$169.82	$169.80	$169.80
Purchase #2	$157.81	4.276%	$164.558	$164.56	$164.55	$164.60
Purchase #3	$72.83	5.235%	$76.6427	$76.64	$76.65	$76.60
Purchase #4	$107.89	5.526%	$113.852	$113.85	$113.85	$113.90
Purchase #5	$78.89	4.211%	$82.2121	$82.21	$82.20	$82.20
Purchase #6	$191.46	11.645%	$213.7555	$213.76	$213.75	$213.80
Purchase #7	$71.26	9.558%	$78.071	$78.07	$78.05	$78.10
7 purchase totals =	$844.65		$898.9133	$898.91	$898.85	$899.00