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	$179.61	9.201%	$196.1359	$196.14	$196.15	$196.10
Purchase #2	$98.36	7.421%	$105.6593	$105.66	$105.65	$105.70
Purchase #3	$224.83	10.845%	$249.2128	$249.21	$249.20	$249.20
Purchase #4	$142.78	7.380%	$153.3172	$153.32	$153.30	$153.30
Purchase #5	$178.90	12.163%	$200.6596	$200.66	$200.65	$200.70
Purchase #6	$66.33	6.241%	$70.4697	$70.47	$70.45	$70.50
Purchase #7	$127.38	4.290%	$132.8446	$132.84	$132.85	$132.80
7 purchase totals =	$1,018.19		$1,108.2991	$1,108.30	$1,108.25	$1,108.30