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	$48.46	3.850%	$50.3257	$50.33	$50.35	$50.30
Purchase #2	$199.99	7.208%	$214.4053	$214.41	$214.40	$214.40
Purchase #3	$89.57	10.667%	$99.1244	$99.12	$99.10	$99.10
Purchase #4	$95.50	8.308%	$103.4341	$103.43	$103.45	$103.40
Purchase #5	$73.42	5.674%	$77.5859	$77.59	$77.60	$77.60
Purchase #6	$19.59	10.195%	$21.5872	$21.59	$21.60	$21.60
Purchase #7	$174.49	9.656%	$191.3388	$191.34	$191.35	$191.30
7 purchase totals =	$701.02		$757.8014	$757.81	$757.85	$757.70