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	$77.93	5.218%	$81.9964	$82.00	$82.00	$82.00
Purchase #2	$226.49	12.817%	$255.5192	$255.52	$255.50	$255.50
Purchase #3	$75.52	3.273%	$77.9918	$77.99	$78.00	$78.00
Purchase #4	$142.63	8.848%	$155.2499	$155.25	$155.25	$155.20
Purchase #5	$22.46	10.686%	$24.8601	$24.86	$24.85	$24.90
Purchase #6	$197.83	13.190%	$223.9238	$223.92	$223.90	$223.90
Purchase #7	$231.60	4.447%	$241.8993	$241.90	$241.90	$241.90
7 purchase totals =	$974.46		$1,061.4405	$1,061.44	$1,061.40	$1,061.40