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	$164.45	9.529%	$180.1204	$180.12	$180.10	$180.10
Purchase #2	$103.38	5.275%	$108.8333	$108.83	$108.85	$108.80
Purchase #3	$191.72	4.752%	$200.8305	$200.83	$200.85	$200.80
Purchase #4	$219.41	9.358%	$239.9424	$239.94	$239.95	$239.90
Purchase #5	$123.89	6.428%	$131.8536	$131.85	$131.85	$131.90
Purchase #6	$174.44	5.822%	$184.5959	$184.60	$184.60	$184.60
Purchase #7	$65.67	6.252%	$69.7757	$69.78	$69.80	$69.80
7 purchase totals =	$1,042.96		$1,115.9518	$1,115.95	$1,116.00	$1,115.90