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	$11.30	5.156%	$11.8826	$11.88	$11.90	$11.90
Purchase #2	$246.48	6.312%	$262.0378	$262.04	$262.05	$262.00
Purchase #3	$74.49	11.305%	$82.9111	$82.91	$82.90	$82.90
Purchase #4	$166.95	3.205%	$172.3007	$172.30	$172.30	$172.30
Purchase #5	$161.53	6.494%	$172.0198	$172.02	$172.00	$172.00
Purchase #6	$127.67	10.137%	$140.6119	$140.61	$140.60	$140.60
Purchase #7	$58.62	10.790%	$64.9451	$64.95	$64.95	$64.90
7 purchase totals =	$847.04		$906.7090	$906.71	$906.70	$906.60