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	$99.36	11.748%	$111.0328	$111.03	$111.05	$111.00
Purchase #2	$245.68	9.474%	$268.9557	$268.96	$268.95	$269.00
Purchase #3	$13.45	6.313%	$14.2991	$14.30	$14.30	$14.30
Purchase #4	$45.71	10.690%	$50.5964	$50.60	$50.60	$50.60
Purchase #5	$172.38	7.468%	$185.2533	$185.25	$185.25	$185.30
Purchase #6	$62.92	10.179%	$69.3246	$69.32	$69.30	$69.30
Purchase #7	$129.43	10.493%	$143.0111	$143.01	$143.00	$143.00
7 purchase totals =	$768.93		$842.4730	$842.47	$842.45	$842.50