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	$233.84	9.560%	$256.1951	$256.20	$256.20	$256.20
Purchase #2	$14.43	6.699%	$15.3967	$15.40	$15.40	$15.40
Purchase #3	$88.83	10.782%	$98.4077	$98.41	$98.40	$98.40
Purchase #4	$234.64	13.109%	$265.399	$265.40	$265.40	$265.40
Purchase #5	$65.71	6.628%	$70.0653	$70.07	$70.05	$70.10
Purchase #6	$195.50	8.830%	$212.7627	$212.76	$212.75	$212.80
Purchase #7	$86.41	4.842%	$90.594	$90.59	$90.60	$90.60
7 purchase totals =	$919.36		$1,008.8205	$1,008.83	$1,008.80	$1,008.90