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	$152.60	7.633%	$164.248	$164.25	$164.25	$164.20
Purchase #2	$142.58	5.412%	$150.2964	$150.30	$150.30	$150.30
Purchase #3	$19.59	7.714%	$21.1012	$21.10	$21.10	$21.10
Purchase #4	$102.85	3.706%	$106.6616	$106.66	$106.65	$106.70
Purchase #5	$209.72	4.383%	$218.912	$218.91	$218.90	$218.90
Purchase #6	$245.95	7.247%	$263.774	$263.77	$263.75	$263.80
Purchase #7	$41.68	4.451%	$43.5352	$43.54	$43.55	$43.50
7 purchase totals =	$914.97		$968.5284	$968.53	$968.50	$968.50