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	$8.62	11.695%	$9.6281	$9.63	$9.65	$9.60
Purchase #2	$233.95	9.141%	$255.3354	$255.34	$255.35	$255.30
Purchase #3	$53.49	11.265%	$59.5156	$59.52	$59.50	$59.50
Purchase #4	$172.32	11.128%	$191.4958	$191.50	$191.50	$191.50
Purchase #5	$162.43	6.458%	$172.9197	$172.92	$172.90	$172.90
Purchase #6	$140.68	5.641%	$148.6158	$148.62	$148.60	$148.60
Purchase #7	$144.65	13.593%	$164.3123	$164.31	$164.30	$164.30
7 purchase totals =	$916.14		$1,001.8227	$1,001.84	$1,001.80	$1,001.70