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	$106.59	10.453%	$117.7319	$117.73	$117.75	$117.70
Purchase #2	$59.79	4.510%	$62.4865	$62.49	$62.50	$62.50
Purchase #3	$23.77	11.164%	$26.4237	$26.42	$26.40	$26.40
Purchase #4	$6.27	5.218%	$6.5972	$6.60	$6.60	$6.60
Purchase #5	$200.30	8.843%	$218.0125	$218.01	$218.00	$218.00
Purchase #6	$162.50	8.223%	$175.8624	$175.86	$175.85	$175.90
Purchase #7	$101.31	4.472%	$105.8406	$105.84	$105.85	$105.80
7 purchase totals =	$660.53		$712.9548	$712.95	$712.95	$712.90