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	$179.95	11.512%	$200.6658	$200.67	$200.65	$200.70
Purchase #2	$163.51	7.296%	$175.4397	$175.44	$175.45	$175.40
Purchase #3	$49.54	10.604%	$54.7932	$54.79	$54.80	$54.80
Purchase #4	$42.25	4.845%	$44.297	$44.30	$44.30	$44.30
Purchase #5	$170.40	12.591%	$191.8551	$191.86	$191.85	$191.90
Purchase #6	$168.73	11.318%	$187.8269	$187.83	$187.85	$187.80
Purchase #7	$38.69	7.243%	$41.4923	$41.49	$41.50	$41.50
7 purchase totals =	$813.07		$896.3700	$896.38	$896.40	$896.40