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	$123.28	4.127%	$128.3678	$128.37	$128.35	$128.40
Purchase #2	$195.29	13.209%	$221.0859	$221.09	$221.10	$221.10
Purchase #3	$171.33	4.805%	$179.5624	$179.56	$179.55	$179.60
Purchase #4	$79.62	7.203%	$85.355	$85.36	$85.35	$85.40
Purchase #5	$111.89	13.443%	$126.9314	$126.93	$126.95	$126.90
Purchase #6	$144.59	9.847%	$158.8278	$158.83	$158.85	$158.80
Purchase #7	$190.64	8.735%	$207.2924	$207.29	$207.30	$207.30
7 purchase totals =	$1,016.64		$1,107.4227	$1,107.43	$1,107.45	$1,107.50