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	$99.77	10.174%	$109.9206	$109.92	$109.90	$109.90
Purchase #2	$213.52	10.780%	$236.5375	$236.54	$236.55	$236.50
Purchase #3	$21.74	12.200%	$24.3923	$24.39	$24.40	$24.40
Purchase #4	$94.72	6.196%	$100.5889	$100.59	$100.60	$100.60
Purchase #5	$180.63	13.742%	$205.4522	$205.45	$205.45	$205.50
Purchase #6	$102.64	9.151%	$112.0326	$112.03	$112.05	$112.00
Purchase #7	$205.90	4.766%	$215.7132	$215.71	$215.70	$215.70
7 purchase totals =	$918.92		$1,004.6373	$1,004.63	$1,004.65	$1,004.60