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	$117.89	8.227%	$127.5888	$127.59	$127.60	$127.60
Purchase #2	$71.48	6.583%	$76.1855	$76.19	$76.20	$76.20
Purchase #3	$45.69	6.281%	$48.5598	$48.56	$48.55	$48.60
Purchase #4	$138.57	10.383%	$152.9577	$152.96	$152.95	$153.00
Purchase #5	$41.35	7.859%	$44.5997	$44.60	$44.60	$44.60
Purchase #6	$245.96	9.555%	$269.4615	$269.46	$269.45	$269.50
Purchase #7	$176.52	13.305%	$200.006	$200.01	$200.00	$200.00
7 purchase totals =	$837.46		$919.3590	$919.37	$919.35	$919.50