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	$115.50	5.548%	$121.9079	$121.91	$121.90	$121.90
Purchase #2	$164.66	5.323%	$173.4249	$173.42	$173.40	$173.40
Purchase #3	$65.29	11.420%	$72.7461	$72.75	$72.75	$72.70
Purchase #4	$22.33	10.198%	$24.6072	$24.61	$24.60	$24.60
Purchase #5	$192.58	12.138%	$215.9554	$215.96	$215.95	$216.00
Purchase #6	$66.92	8.150%	$72.374	$72.37	$72.35	$72.40
Purchase #7	$74.27	11.258%	$82.6313	$82.63	$82.65	$82.60
7 purchase totals =	$701.55		$763.6468	$763.65	$763.60	$763.60