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	$43.41	11.316%	$48.3223	$48.32	$48.30	$48.30
Purchase #2	$34.30	9.319%	$37.4964	$37.50	$37.50	$37.50
Purchase #3	$111.99	5.665%	$118.3342	$118.33	$118.35	$118.30
Purchase #4	$14.82	9.370%	$16.2086	$16.21	$16.20	$16.20
Purchase #5	$109.90	12.526%	$123.6661	$123.67	$123.65	$123.70
Purchase #6	$242.86	12.798%	$273.9412	$273.94	$273.95	$273.90
Purchase #7	$73.98	12.160%	$82.976	$82.98	$83.00	$83.00
7 purchase totals =	$631.26		$700.9448	$700.95	$700.95	$700.90