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	$77.35	3.811%	$80.2978	$80.30	$80.30	$80.30
Purchase #2	$221.37	12.559%	$249.1719	$249.17	$249.15	$249.20
Purchase #3	$208.39	4.547%	$217.8655	$217.87	$217.85	$217.90
Purchase #4	$113.62	12.219%	$127.5032	$127.50	$127.50	$127.50
Purchase #5	$115.99	12.536%	$130.5305	$130.53	$130.55	$130.50
Purchase #6	$67.33	4.341%	$70.2528	$70.25	$70.25	$70.30
Purchase #7	$117.82	13.615%	$133.8612	$133.86	$133.85	$133.90
7 purchase totals =	$921.87		$1,009.4829	$1,009.48	$1,009.45	$1,009.60