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	$231.38	10.794%	$256.3552	$256.36	$256.35	$256.40
Purchase #2	$79.78	9.538%	$87.3894	$87.39	$87.40	$87.40
Purchase #3	$121.78	12.472%	$136.9684	$136.97	$136.95	$137.00
Purchase #4	$243.88	9.392%	$266.7852	$266.79	$266.80	$266.80
Purchase #5	$162.54	10.400%	$179.4442	$179.44	$179.45	$179.40
Purchase #6	$224.33	6.383%	$238.649	$238.65	$238.65	$238.60
Purchase #7	$90.33	6.759%	$96.4354	$96.44	$96.45	$96.40
7 purchase totals =	$1,154.02		$1,262.0268	$1,262.04	$1,262.05	$1,262.00