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	$233.56	5.823%	$247.1602	$247.16	$247.15	$247.20
Purchase #2	$170.60	9.576%	$186.9367	$186.94	$186.95	$186.90
Purchase #3	$209.94	8.719%	$228.2447	$228.24	$228.25	$228.20
Purchase #4	$245.62	4.203%	$255.9434	$255.94	$255.95	$255.90
Purchase #5	$5.50	9.306%	$6.0118	$6.01	$6.00	$6.00
Purchase #6	$55.93	9.696%	$61.353	$61.35	$61.35	$61.40
Purchase #7	$31.77	6.470%	$33.8255	$33.83	$33.85	$33.80
7 purchase totals =	$952.92		$1,019.4753	$1,019.47	$1,019.50	$1,019.40