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	$61.74	4.639%	$64.6041	$64.60	$64.60	$64.60
Purchase #2	$244.44	3.153%	$252.1472	$252.15	$252.15	$252.10
Purchase #3	$130.39	13.133%	$147.5141	$147.51	$147.50	$147.50
Purchase #4	$172.98	5.150%	$181.8885	$181.89	$181.90	$181.90
Purchase #5	$78.89	6.408%	$83.9453	$83.95	$83.95	$83.90
Purchase #6	$77.71	10.792%	$86.0965	$86.10	$86.10	$86.10
Purchase #7	$54.86	9.157%	$59.8835	$59.88	$59.90	$59.90
7 purchase totals =	$821.01		$876.0792	$876.08	$876.10	$876.00