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	$64.32	10.697%	$71.2003	$71.20	$71.20	$71.20
Purchase #2	$152.42	13.307%	$172.7025	$172.70	$172.70	$172.70
Purchase #3	$178.69	6.220%	$189.8045	$189.80	$189.80	$189.80
Purchase #4	$144.94	6.102%	$153.7842	$153.78	$153.80	$153.80
Purchase #5	$63.83	5.734%	$67.49	$67.49	$67.50	$67.50
Purchase #6	$250.39	9.203%	$273.4334	$273.43	$273.45	$273.40
Purchase #7	$67.84	5.706%	$71.711	$71.71	$71.70	$71.70
7 purchase totals =	$922.43		$1,000.1259	$1,000.11	$1,000.15	$1,000.10