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	$133.71	12.579%	$150.5294	$150.53	$150.55	$150.50
Purchase #2	$168.47	8.346%	$182.5305	$182.53	$182.55	$182.50
Purchase #3	$148.77	10.475%	$164.3537	$164.35	$164.35	$164.40
Purchase #4	$67.84	5.766%	$71.7517	$71.75	$71.75	$71.80
Purchase #5	$245.41	9.149%	$267.8626	$267.86	$267.85	$267.90
Purchase #6	$116.82	3.525%	$120.9379	$120.94	$120.95	$120.90
Purchase #7	$171.32	9.321%	$187.2887	$187.29	$187.30	$187.30
7 purchase totals =	$1,052.34		$1,145.2545	$1,145.25	$1,145.30	$1,145.30