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	$62.84	13.718%	$71.4604	$71.46	$71.45	$71.50
Purchase #2	$217.54	12.299%	$244.2952	$244.30	$244.30	$244.30
Purchase #3	$131.57	8.404%	$142.6271	$142.63	$142.65	$142.60
Purchase #4	$204.34	8.184%	$221.0632	$221.06	$221.05	$221.10
Purchase #5	$116.94	13.300%	$132.493	$132.49	$132.50	$132.50
Purchase #6	$232.25	9.868%	$255.1684	$255.17	$255.15	$255.20
Purchase #7	$71.57	5.508%	$75.5121	$75.51	$75.50	$75.50
7 purchase totals =	$1,037.05		$1,142.6194	$1,142.62	$1,142.60	$1,142.70