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	$141.25	3.193%	$145.7601	$145.76	$145.75	$145.80
Purchase #2	$101.97	4.339%	$106.3945	$106.39	$106.40	$106.40
Purchase #3	$163.91	9.352%	$179.2389	$179.24	$179.25	$179.20
Purchase #4	$157.57	6.182%	$167.311	$167.31	$167.30	$167.30
Purchase #5	$162.62	6.354%	$172.9529	$172.95	$172.95	$173.00
Purchase #6	$85.49	5.560%	$90.2432	$90.24	$90.25	$90.20
Purchase #7	$90.88	13.406%	$103.0634	$103.06	$103.05	$103.10
7 purchase totals =	$903.69		$964.9640	$964.95	$964.95	$965.00