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	$111.84	5.112%	$117.5573	$117.56	$117.55	$117.60
Purchase #2	$53.90	9.218%	$58.8685	$58.87	$58.85	$58.90
Purchase #3	$221.32	6.744%	$236.2458	$236.25	$236.25	$236.20
Purchase #4	$177.57	8.442%	$192.5605	$192.56	$192.55	$192.60
Purchase #5	$227.87	7.772%	$245.5801	$245.58	$245.60	$245.60
Purchase #6	$19.45	11.331%	$21.6539	$21.65	$21.65	$21.70
Purchase #7	$128.87	12.109%	$144.4749	$144.47	$144.45	$144.50
7 purchase totals =	$940.82		$1,016.9410	$1,016.94	$1,016.90	$1,017.10