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	$243.90	8.579%	$264.8242	$264.82	$264.80	$264.80
Purchase #2	$171.87	7.760%	$185.2071	$185.21	$185.20	$185.20
Purchase #3	$18.90	11.812%	$21.1325	$21.13	$21.15	$21.10
Purchase #4	$164.58	4.183%	$171.4644	$171.46	$171.45	$171.50
Purchase #5	$126.42	11.475%	$140.9267	$140.93	$140.95	$140.90
Purchase #6	$69.49	3.652%	$72.0278	$72.03	$72.05	$72.00
Purchase #7	$173.55	7.325%	$186.2625	$186.26	$186.25	$186.30
7 purchase totals =	$968.71		$1,041.8452	$1,041.84	$1,041.85	$1,041.80