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	$92.29	4.341%	$96.2963	$96.30	$96.30	$96.30
Purchase #2	$130.59	13.707%	$148.49	$148.49	$148.50	$148.50
Purchase #3	$86.95	13.509%	$98.6961	$98.70	$98.70	$98.70
Purchase #4	$43.54	10.310%	$48.029	$48.03	$48.05	$48.00
Purchase #5	$52.90	12.108%	$59.3051	$59.31	$59.30	$59.30
Purchase #6	$201.82	13.423%	$228.9103	$228.91	$228.90	$228.90
Purchase #7	$60.94	9.339%	$66.6312	$66.63	$66.65	$66.60
7 purchase totals =	$669.03		$746.3580	$746.37	$746.40	$746.30