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	$72.28	3.230%	$74.6146	$74.61	$74.60	$74.60
Purchase #2	$143.58	12.158%	$161.0365	$161.04	$161.05	$161.00
Purchase #3	$12.61	7.729%	$13.5846	$13.58	$13.60	$13.60
Purchase #4	$115.69	3.216%	$119.4106	$119.41	$119.40	$119.40
Purchase #5	$164.32	7.429%	$176.5273	$176.53	$176.55	$176.50
Purchase #6	$196.50	4.402%	$205.1499	$205.15	$205.15	$205.10
Purchase #7	$57.33	3.319%	$59.2328	$59.23	$59.25	$59.20
7 purchase totals =	$762.31		$809.5563	$809.55	$809.60	$809.40