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	$160.62	7.324%	$172.3838	$172.38	$172.40	$172.40
Purchase #2	$58.32	7.523%	$62.7074	$62.71	$62.70	$62.70
Purchase #3	$73.77	13.143%	$83.4656	$83.47	$83.45	$83.50
Purchase #4	$190.65	3.133%	$196.6231	$196.62	$196.60	$196.60
Purchase #5	$153.28	9.609%	$168.0087	$168.01	$168.00	$168.00
Purchase #6	$210.58	4.150%	$219.3191	$219.32	$219.30	$219.30
Purchase #7	$70.61	13.191%	$79.9242	$79.92	$79.90	$79.90
7 purchase totals =	$917.83		$982.4319	$982.43	$982.35	$982.40