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	$51.54	11.452%	$57.4424	$57.44	$57.45	$57.40
Purchase #2	$125.38	7.556%	$134.8537	$134.85	$134.85	$134.90
Purchase #3	$111.32	4.278%	$116.0823	$116.08	$116.10	$116.10
Purchase #4	$84.61	7.370%	$90.8458	$90.85	$90.85	$90.80
Purchase #5	$30.37	6.582%	$32.369	$32.37	$32.35	$32.40
Purchase #6	$155.42	13.109%	$175.794	$175.79	$175.80	$175.80
Purchase #7	$240.48	10.401%	$265.4923	$265.49	$265.50	$265.50
7 purchase totals =	$799.12		$872.8795	$872.87	$872.90	$872.90