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	$108.46	11.146%	$120.549	$120.55	$120.55	$120.50
Purchase #2	$154.78	8.288%	$167.6082	$167.61	$167.60	$167.60
Purchase #3	$142.45	13.590%	$161.809	$161.81	$161.80	$161.80
Purchase #4	$98.79	4.562%	$103.2968	$103.30	$103.30	$103.30
Purchase #5	$247.83	6.857%	$264.8237	$264.82	$264.80	$264.80
Purchase #6	$16.76	6.393%	$17.8315	$17.83	$17.85	$17.80
Purchase #7	$177.82	10.434%	$196.3737	$196.37	$196.35	$196.40
7 purchase totals =	$946.89		$1,032.2919	$1,032.29	$1,032.25	$1,032.20