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	$158.52	5.805%	$167.7221	$167.72	$167.70	$167.70
Purchase #2	$191.47	11.238%	$212.9874	$212.99	$213.00	$213.00
Purchase #3	$103.80	7.794%	$111.8902	$111.89	$111.90	$111.90
Purchase #4	$68.68	10.531%	$75.9127	$75.91	$75.90	$75.90
Purchase #5	$47.61	10.437%	$52.5791	$52.58	$52.60	$52.60
Purchase #6	$241.81	12.698%	$272.515	$272.52	$272.50	$272.50
Purchase #7	$31.42	3.274%	$32.4487	$32.45	$32.45	$32.40
7 purchase totals =	$843.31		$926.0552	$926.06	$926.05	$926.00