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	$109.45	4.710%	$114.6051	$114.61	$114.60	$114.60
Purchase #2	$94.90	3.182%	$97.9197	$97.92	$97.90	$97.90
Purchase #3	$144.56	7.140%	$154.8816	$154.88	$154.90	$154.90
Purchase #4	$161.64	4.391%	$168.7376	$168.74	$168.75	$168.70
Purchase #5	$99.95	4.421%	$104.3688	$104.37	$104.35	$104.40
Purchase #6	$52.94	4.786%	$55.4737	$55.47	$55.45	$55.50
Purchase #7	$143.74	11.448%	$160.1954	$160.20	$160.20	$160.20
7 purchase totals =	$807.18		$856.1819	$856.19	$856.15	$856.20