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	$125.35	11.557%	$139.8367	$139.84	$139.85	$139.80
Purchase #2	$11.28	9.785%	$12.3837	$12.38	$12.40	$12.40
Purchase #3	$228.83	6.139%	$242.8779	$242.88	$242.90	$242.90
Purchase #4	$249.41	10.683%	$276.0545	$276.05	$276.05	$276.10
Purchase #5	$71.48	13.579%	$81.1863	$81.19	$81.20	$81.20
Purchase #6	$143.84	4.579%	$150.4264	$150.43	$150.45	$150.40
Purchase #7	$178.27	6.801%	$190.3941	$190.39	$190.40	$190.40
7 purchase totals =	$1,008.46		$1,093.1596	$1,093.16	$1,093.25	$1,093.20