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	$29.44	9.315%	$32.1823	$32.18	$32.20	$32.20
Purchase #2	$85.97	4.472%	$89.8146	$89.81	$89.80	$89.80
Purchase #3	$161.60	5.163%	$169.9434	$169.94	$169.95	$169.90
Purchase #4	$136.45	11.711%	$152.4297	$152.43	$152.45	$152.40
Purchase #5	$226.33	4.379%	$236.241	$236.24	$236.25	$236.20
Purchase #6	$157.49	5.528%	$166.196	$166.20	$166.20	$166.20
Purchase #7	$229.89	3.767%	$238.55	$238.55	$238.55	$238.60
7 purchase totals =	$1,027.17		$1,085.3570	$1,085.35	$1,085.40	$1,085.30