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	$211.86	5.150%	$222.7708	$222.77	$222.75	$222.80
Purchase #2	$16.72	10.728%	$18.5137	$18.51	$18.50	$18.50
Purchase #3	$150.32	8.292%	$162.7845	$162.78	$162.80	$162.80
Purchase #4	$46.92	3.270%	$48.4543	$48.45	$48.45	$48.50
Purchase #5	$122.48	6.469%	$130.4032	$130.40	$130.40	$130.40
Purchase #6	$196.98	6.818%	$210.4101	$210.41	$210.40	$210.40
Purchase #7	$111.29	11.551%	$124.1451	$124.15	$124.15	$124.10
7 purchase totals =	$856.57		$917.4817	$917.47	$917.45	$917.50