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	$207.76	5.211%	$218.5864	$218.59	$218.60	$218.60
Purchase #2	$136.42	10.754%	$151.0906	$151.09	$151.10	$151.10
Purchase #3	$135.98	4.679%	$142.3425	$142.34	$142.35	$142.30
Purchase #4	$117.53	12.834%	$132.6138	$132.61	$132.60	$132.60
Purchase #5	$149.57	11.219%	$166.3503	$166.35	$166.35	$166.40
Purchase #6	$151.90	13.230%	$171.9964	$172.00	$172.00	$172.00
Purchase #7	$38.27	8.670%	$41.588	$41.59	$41.60	$41.60
7 purchase totals =	$937.43		$1,024.5680	$1,024.57	$1,024.60	$1,024.60