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	$74.52	10.115%	$82.0577	$82.06	$82.05	$82.10
Purchase #2	$128.84	10.470%	$142.3295	$142.33	$142.35	$142.30
Purchase #3	$23.38	10.693%	$25.88	$25.88	$25.90	$25.90
Purchase #4	$48.96	6.859%	$52.3182	$52.32	$52.30	$52.30
Purchase #5	$99.85	3.508%	$103.3527	$103.35	$103.35	$103.40
Purchase #6	$33.81	3.553%	$35.0113	$35.01	$35.00	$35.00
Purchase #7	$113.32	3.476%	$117.259	$117.26	$117.25	$117.30
7 purchase totals =	$522.68		$558.2084	$558.21	$558.20	$558.30