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	$137.96	3.268%	$142.4685	$142.47	$142.45	$142.50
Purchase #2	$158.40	9.343%	$173.1993	$173.20	$173.20	$173.20
Purchase #3	$132.61	10.829%	$146.9703	$146.97	$146.95	$147.00
Purchase #4	$92.94	11.349%	$103.4878	$103.49	$103.50	$103.50
Purchase #5	$156.62	8.644%	$170.1582	$170.16	$170.15	$170.20
Purchase #6	$140.34	11.682%	$156.7345	$156.73	$156.75	$156.70
Purchase #7	$113.29	9.308%	$123.835	$123.84	$123.85	$123.80
7 purchase totals =	$932.16		$1,016.8536	$1,016.86	$1,016.85	$1,016.90