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	$43.49	8.770%	$47.3041	$47.30	$47.30	$47.30
Purchase #2	$181.38	8.534%	$196.859	$196.86	$196.85	$196.90
Purchase #3	$68.29	11.598%	$76.2103	$76.21	$76.20	$76.20
Purchase #4	$68.49	5.656%	$72.3638	$72.36	$72.35	$72.40
Purchase #5	$112.33	13.813%	$127.8461	$127.85	$127.85	$127.80
Purchase #6	$204.71	9.506%	$224.1697	$224.17	$224.15	$224.20
Purchase #7	$51.31	10.625%	$56.7617	$56.76	$56.75	$56.80
7 purchase totals =	$730.00		$801.5147	$801.51	$801.45	$801.60