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	$205.36	6.180%	$218.0512	$218.05	$218.05	$218.10
Purchase #2	$38.95	12.126%	$43.6731	$43.67	$43.65	$43.70
Purchase #3	$149.39	4.498%	$156.1096	$156.11	$156.10	$156.10
Purchase #4	$188.35	11.798%	$210.5715	$210.57	$210.55	$210.60
Purchase #5	$196.89	10.448%	$217.4611	$217.46	$217.45	$217.50
Purchase #6	$175.69	8.362%	$190.3812	$190.38	$190.40	$190.40
Purchase #7	$144.39	13.848%	$164.3851	$164.39	$164.40	$164.40
7 purchase totals =	$1,099.02		$1,200.6328	$1,200.63	$1,200.60	$1,200.80