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	$192.40	4.764%	$201.5659	$201.57	$201.55	$201.60
Purchase #2	$117.62	8.706%	$127.86	$127.86	$127.85	$127.90
Purchase #3	$218.75	8.490%	$237.3219	$237.32	$237.30	$237.30
Purchase #4	$43.49	11.596%	$48.5331	$48.53	$48.55	$48.50
Purchase #5	$62.71	7.525%	$67.4289	$67.43	$67.45	$67.40
Purchase #6	$224.46	13.598%	$254.9821	$254.98	$255.00	$255.00
Purchase #7	$59.72	4.587%	$62.4594	$62.46	$62.45	$62.50
7 purchase totals =	$919.15		$1,000.1513	$1,000.15	$1,000.15	$1,000.20