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	$106.43	9.540%	$116.5834	$116.58	$116.60	$116.60
Purchase #2	$249.95	5.459%	$263.5948	$263.59	$263.60	$263.60
Purchase #3	$151.38	3.599%	$156.8282	$156.83	$156.85	$156.80
Purchase #4	$52.40	12.813%	$59.114	$59.11	$59.10	$59.10
Purchase #5	$151.48	10.142%	$166.8431	$166.84	$166.85	$166.80
Purchase #6	$109.78	10.229%	$121.0094	$121.01	$121.00	$121.00
Purchase #7	$163.28	8.591%	$177.3074	$177.31	$177.30	$177.30
7 purchase totals =	$984.70		$1,061.2803	$1,061.27	$1,061.30	$1,061.20