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	$133.89	7.538%	$143.9826	$143.98	$144.00	$144.00
Purchase #2	$18.95	9.661%	$20.7808	$20.78	$20.80	$20.80
Purchase #3	$33.97	6.645%	$36.2273	$36.23	$36.25	$36.20
Purchase #4	$20.41	4.324%	$21.2925	$21.29	$21.30	$21.30
Purchase #5	$170.41	3.364%	$176.1426	$176.14	$176.15	$176.10
Purchase #6	$34.92	10.344%	$38.5321	$38.53	$38.55	$38.50
Purchase #7	$84.62	6.656%	$90.2523	$90.25	$90.25	$90.30
7 purchase totals =	$497.17		$527.2102	$527.20	$527.30	$527.20