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	$134.81	5.597%	$142.3553	$142.36	$142.35	$142.40
Purchase #2	$201.59	9.603%	$220.9487	$220.95	$220.95	$220.90
Purchase #3	$41.84	5.314%	$44.0634	$44.06	$44.05	$44.10
Purchase #4	$116.39	6.158%	$123.5573	$123.56	$123.55	$123.60
Purchase #5	$141.33	8.574%	$153.4476	$153.45	$153.45	$153.40
Purchase #6	$100.32	3.833%	$104.1653	$104.17	$104.15	$104.20
Purchase #7	$224.75	7.820%	$242.3255	$242.33	$242.35	$242.30
7 purchase totals =	$961.03		$1,030.8631	$1,030.88	$1,030.85	$1,030.90