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	$53.60	3.421%	$55.4337	$55.43	$55.45	$55.40
Purchase #2	$151.81	7.280%	$162.8618	$162.86	$162.85	$162.90
Purchase #3	$77.98	4.262%	$81.3035	$81.30	$81.30	$81.30
Purchase #4	$115.37	9.383%	$126.1952	$126.20	$126.20	$126.20
Purchase #5	$217.51	11.618%	$242.7803	$242.78	$242.80	$242.80
Purchase #6	$99.76	11.705%	$111.4369	$111.44	$111.45	$111.40
Purchase #7	$6.51	6.259%	$6.9175	$6.92	$6.90	$6.90
7 purchase totals =	$722.54		$786.9289	$786.93	$786.95	$786.90