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	$126.51	8.389%	$137.1229	$137.12	$137.10	$137.10
Purchase #2	$127.67	9.291%	$139.5318	$139.53	$139.55	$139.50
Purchase #3	$38.52	13.340%	$43.6586	$43.66	$43.65	$43.70
Purchase #4	$238.95	5.671%	$252.5009	$252.50	$252.50	$252.50
Purchase #5	$193.60	11.345%	$215.5639	$215.56	$215.55	$215.60
Purchase #6	$54.62	9.786%	$59.9651	$59.97	$59.95	$60.00
Purchase #7	$219.29	7.756%	$236.2981	$236.30	$236.30	$236.30
7 purchase totals =	$999.16		$1,084.6413	$1,084.64	$1,084.60	$1,084.70