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	$65.78	4.298%	$68.6072	$68.61	$68.60	$68.60
Purchase #2	$240.25	12.581%	$270.4759	$270.48	$270.50	$270.50
Purchase #3	$37.86	9.870%	$41.5968	$41.60	$41.60	$41.60
Purchase #4	$216.38	11.799%	$241.9107	$241.91	$241.90	$241.90
Purchase #5	$194.42	11.704%	$217.1749	$217.17	$217.15	$217.20
Purchase #6	$6.32	12.670%	$7.1207	$7.12	$7.10	$7.10
Purchase #7	$111.39	10.408%	$122.9835	$122.98	$123.00	$123.00
7 purchase totals =	$872.40		$969.8697	$969.87	$969.85	$969.90