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	$215.77	12.503%	$242.7477	$242.75	$242.75	$242.70
Purchase #2	$50.39	10.268%	$55.564	$55.56	$55.55	$55.60
Purchase #3	$113.98	12.745%	$128.5068	$128.51	$128.50	$128.50
Purchase #4	$130.92	13.602%	$148.7277	$148.73	$148.75	$148.70
Purchase #5	$116.51	5.672%	$123.1184	$123.12	$123.10	$123.10
Purchase #6	$116.47	11.788%	$130.1995	$130.20	$130.20	$130.20
Purchase #7	$232.77	9.737%	$255.4348	$255.43	$255.45	$255.40
7 purchase totals =	$976.81		$1,084.2989	$1,084.30	$1,084.30	$1,084.20