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	$103.43	13.107%	$116.9866	$116.99	$117.00	$117.00
Purchase #2	$194.98	3.573%	$201.9466	$201.95	$201.95	$201.90
Purchase #3	$116.57	9.210%	$127.3061	$127.31	$127.30	$127.30
Purchase #4	$51.66	13.164%	$58.4605	$58.46	$58.45	$58.50
Purchase #5	$146.60	3.865%	$152.2661	$152.27	$152.25	$152.30
Purchase #6	$87.67	9.173%	$95.712	$95.71	$95.70	$95.70
Purchase #7	$246.64	3.518%	$255.3168	$255.32	$255.30	$255.30
7 purchase totals =	$947.55		$1,007.9947	$1,008.01	$1,007.95	$1,008.00