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	$40.89	11.193%	$45.4668	$45.47	$45.45	$45.50
Purchase #2	$163.96	9.289%	$179.1902	$179.19	$179.20	$179.20
Purchase #3	$156.85	5.638%	$165.6932	$165.69	$165.70	$165.70
Purchase #4	$57.84	10.303%	$63.7993	$63.80	$63.80	$63.80
Purchase #5	$142.91	9.742%	$156.8323	$156.83	$156.85	$156.80
Purchase #6	$100.95	3.444%	$104.4267	$104.43	$104.45	$104.40
Purchase #7	$29.66	8.812%	$32.2736	$32.27	$32.25	$32.30
7 purchase totals =	$693.06		$747.6821	$747.68	$747.70	$747.70