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	$205.46	8.824%	$223.5898	$223.59	$223.60	$223.60
Purchase #2	$147.91	10.189%	$162.9805	$162.98	$163.00	$163.00
Purchase #3	$80.40	6.436%	$85.5745	$85.57	$85.55	$85.60
Purchase #4	$230.79	6.221%	$245.1474	$245.15	$245.15	$245.10
Purchase #5	$26.42	5.687%	$27.9225	$27.92	$27.90	$27.90
Purchase #6	$143.89	6.234%	$152.8601	$152.86	$152.85	$152.90
Purchase #7	$242.77	8.215%	$262.7136	$262.71	$262.70	$262.70
7 purchase totals =	$1,077.64		$1,160.7884	$1,160.78	$1,160.75	$1,160.80