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	$193.50	8.650%	$210.2378	$210.24	$210.25	$210.20
Purchase #2	$238.58	12.320%	$267.9731	$267.97	$267.95	$268.00
Purchase #3	$47.73	9.705%	$52.3622	$52.36	$52.35	$52.40
Purchase #4	$124.60	9.852%	$136.8756	$136.88	$136.90	$136.90
Purchase #5	$29.51	10.309%	$32.5522	$32.55	$32.55	$32.60
Purchase #6	$208.40	12.230%	$233.8873	$233.89	$233.90	$233.90
Purchase #7	$125.42	5.715%	$132.5878	$132.59	$132.60	$132.60
7 purchase totals =	$967.74		$1,066.4760	$1,066.48	$1,066.50	$1,066.60