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	$149.92	9.738%	$164.5192	$164.52	$164.50	$164.50
Purchase #2	$86.51	6.258%	$91.9238	$91.92	$91.90	$91.90
Purchase #3	$228.83	11.380%	$254.8709	$254.87	$254.85	$254.90
Purchase #4	$182.38	11.561%	$203.465	$203.47	$203.45	$203.50
Purchase #5	$73.36	3.797%	$76.1455	$76.15	$76.15	$76.10
Purchase #6	$244.34	10.506%	$270.0104	$270.01	$270.00	$270.00
Purchase #7	$6.81	7.357%	$7.311	$7.31	$7.30	$7.30
7 purchase totals =	$972.15		$1,068.2458	$1,068.25	$1,068.15	$1,068.20