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	$22.30	10.729%	$24.6926	$24.69	$24.70	$24.70
Purchase #2	$104.33	11.655%	$116.4897	$116.49	$116.50	$116.50
Purchase #3	$152.78	7.593%	$164.3806	$164.38	$164.40	$164.40
Purchase #4	$67.66	7.307%	$72.6039	$72.60	$72.60	$72.60
Purchase #5	$70.84	13.407%	$80.3375	$80.34	$80.35	$80.30
Purchase #6	$118.33	11.353%	$131.764	$131.76	$131.75	$131.80
Purchase #7	$110.93	3.406%	$114.7083	$114.71	$114.70	$114.70
7 purchase totals =	$647.17		$704.9766	$704.97	$705.00	$705.00