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	$206.30	6.161%	$219.0101	$219.01	$219.00	$219.00
Purchase #2	$166.98	5.151%	$175.5811	$175.58	$175.60	$175.60
Purchase #3	$104.45	4.408%	$109.0542	$109.05	$109.05	$109.10
Purchase #4	$238.36	11.433%	$265.6117	$265.61	$265.60	$265.60
Purchase #5	$151.88	6.679%	$162.0241	$162.02	$162.00	$162.00
Purchase #6	$154.96	13.855%	$176.4297	$176.43	$176.45	$176.40
Purchase #7	$33.25	9.401%	$36.3758	$36.38	$36.40	$36.40
7 purchase totals =	$1,056.18		$1,144.0867	$1,144.08	$1,144.10	$1,144.10