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	$81.42	6.192%	$86.4615	$86.46	$86.45	$86.50
Purchase #2	$50.44	7.495%	$54.2205	$54.22	$54.20	$54.20
Purchase #3	$35.66	12.631%	$40.1642	$40.16	$40.15	$40.20
Purchase #4	$221.49	12.629%	$249.462	$249.46	$249.45	$249.50
Purchase #5	$100.27	10.735%	$111.034	$111.03	$111.05	$111.00
Purchase #6	$243.32	5.390%	$256.4349	$256.43	$256.45	$256.40
Purchase #7	$86.75	12.506%	$97.599	$97.60	$97.60	$97.60
7 purchase totals =	$819.35		$895.3761	$895.36	$895.35	$895.40