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	$81.53	10.505%	$90.0947	$90.09	$90.10	$90.10
Purchase #2	$34.60	11.504%	$38.5804	$38.58	$38.60	$38.60
Purchase #3	$192.26	11.236%	$213.8623	$213.86	$213.85	$213.90
Purchase #4	$118.77	8.106%	$128.3975	$128.40	$128.40	$128.40
Purchase #5	$154.66	5.174%	$162.6621	$162.66	$162.65	$162.70
Purchase #6	$233.39	8.202%	$252.5326	$252.53	$252.55	$252.50
Purchase #7	$165.31	5.773%	$174.8533	$174.85	$174.85	$174.90
7 purchase totals =	$980.52		$1,060.9829	$1,060.97	$1,061.00	$1,061.10