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	$90.60	4.762%	$94.9144	$94.91	$94.90	$94.90
Purchase #2	$153.61	10.356%	$169.5179	$169.52	$169.50	$169.50
Purchase #3	$136.40	11.415%	$151.9701	$151.97	$151.95	$152.00
Purchase #4	$155.98	7.230%	$167.2574	$167.26	$167.25	$167.30
Purchase #5	$151.74	7.253%	$162.7457	$162.75	$162.75	$162.70
Purchase #6	$220.51	10.614%	$243.9149	$243.91	$243.90	$243.90
Purchase #7	$112.83	3.160%	$116.3954	$116.40	$116.40	$116.40
7 purchase totals =	$1,021.67		$1,106.7158	$1,106.72	$1,106.65	$1,106.70