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	$79.47	4.209%	$82.8149	$82.81	$82.80	$82.80
Purchase #2	$94.44	11.326%	$105.1363	$105.14	$105.15	$105.10
Purchase #3	$123.63	4.115%	$128.7174	$128.72	$128.70	$128.70
Purchase #4	$231.38	10.293%	$255.1959	$255.20	$255.20	$255.20
Purchase #5	$145.30	13.288%	$164.6075	$164.61	$164.60	$164.60
Purchase #6	$232.54	3.466%	$240.5998	$240.60	$240.60	$240.60
Purchase #7	$34.77	3.313%	$35.9219	$35.92	$35.90	$35.90
7 purchase totals =	$941.53		$1,012.9937	$1,013.00	$1,012.95	$1,012.90