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	$136.43	8.341%	$147.8096	$147.81	$147.80	$147.80
Purchase #2	$109.79	8.522%	$119.1463	$119.15	$119.15	$119.10
Purchase #3	$175.72	12.771%	$198.1612	$198.16	$198.15	$198.20
Purchase #4	$74.40	11.119%	$82.6725	$82.67	$82.65	$82.70
Purchase #5	$34.58	7.387%	$37.1344	$37.13	$37.15	$37.10
Purchase #6	$199.70	9.655%	$218.981	$218.98	$219.00	$219.00
Purchase #7	$194.67	7.677%	$209.6148	$209.61	$209.60	$209.60
7 purchase totals =	$925.29		$1,013.5198	$1,013.51	$1,013.50	$1,013.50