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	$195.45	11.584%	$218.0909	$218.09	$218.10	$218.10
Purchase #2	$32.89	6.304%	$34.9634	$34.96	$34.95	$35.00
Purchase #3	$81.28	10.715%	$89.9892	$89.99	$90.00	$90.00
Purchase #4	$11.93	5.542%	$12.5912	$12.59	$12.60	$12.60
Purchase #5	$174.81	9.547%	$191.4991	$191.50	$191.50	$191.50
Purchase #6	$127.59	9.459%	$139.6587	$139.66	$139.65	$139.70
Purchase #7	$212.30	12.448%	$238.7271	$238.73	$238.75	$238.70
7 purchase totals =	$836.25		$925.5196	$925.52	$925.55	$925.60