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	$184.92	3.710%	$191.7805	$191.78	$191.80	$191.80
Purchase #2	$158.33	11.212%	$176.082	$176.08	$176.10	$176.10
Purchase #3	$231.61	3.110%	$238.8131	$238.81	$238.80	$238.80
Purchase #4	$36.86	11.330%	$41.0362	$41.04	$41.05	$41.00
Purchase #5	$53.73	11.160%	$59.7263	$59.73	$59.75	$59.70
Purchase #6	$124.97	10.331%	$137.8807	$137.88	$137.90	$137.90
Purchase #7	$163.81	7.798%	$176.5839	$176.58	$176.60	$176.60
7 purchase totals =	$954.23		$1,021.9027	$1,021.90	$1,022.00	$1,021.90