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	$228.32	7.296%	$244.9782	$244.98	$245.00	$245.00
Purchase #2	$145.32	3.710%	$150.7114	$150.71	$150.70	$150.70
Purchase #3	$137.90	3.640%	$142.9196	$142.92	$142.90	$142.90
Purchase #4	$107.52	11.484%	$119.8676	$119.87	$119.85	$119.90
Purchase #5	$9.66	12.558%	$10.8731	$10.87	$10.85	$10.90
Purchase #6	$20.48	6.807%	$21.8741	$21.87	$21.85	$21.90
Purchase #7	$18.66	4.629%	$19.5238	$19.52	$19.50	$19.50
7 purchase totals =	$667.86		$710.7478	$710.74	$710.65	$710.80