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	$208.79	4.725%	$218.6553	$218.66	$218.65	$218.70
Purchase #2	$143.63	10.248%	$158.3492	$158.35	$158.35	$158.30
Purchase #3	$44.81	12.743%	$50.5201	$50.52	$50.50	$50.50
Purchase #4	$183.28	9.142%	$200.0355	$200.04	$200.05	$200.00
Purchase #5	$119.52	3.425%	$123.6136	$123.61	$123.60	$123.60
Purchase #6	$238.88	12.407%	$268.5178	$268.52	$268.50	$268.50
Purchase #7	$54.97	6.109%	$58.3281	$58.33	$58.35	$58.30
7 purchase totals =	$993.88		$1,078.0196	$1,078.03	$1,078.00	$1,077.90