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	$245.32	7.622%	$264.0183	$264.02	$264.00	$264.00
Purchase #2	$233.65	9.263%	$255.293	$255.29	$255.30	$255.30
Purchase #3	$112.57	13.872%	$128.1857	$128.19	$128.20	$128.20
Purchase #4	$164.68	8.482%	$178.6482	$178.65	$178.65	$178.60
Purchase #5	$51.45	3.222%	$53.1077	$53.11	$53.10	$53.10
Purchase #6	$85.75	3.849%	$89.0505	$89.05	$89.05	$89.10
Purchase #7	$76.47	6.372%	$81.3427	$81.34	$81.35	$81.30
7 purchase totals =	$969.89		$1,049.6461	$1,049.65	$1,049.65	$1,049.60