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	$95.68	13.547%	$108.6418	$108.64	$108.65	$108.60
Purchase #2	$235.95	11.604%	$263.3296	$263.33	$263.35	$263.30
Purchase #3	$188.45	4.293%	$196.5402	$196.54	$196.55	$196.50
Purchase #4	$181.46	13.835%	$206.565	$206.57	$206.55	$206.60
Purchase #5	$119.40	13.443%	$135.4509	$135.45	$135.45	$135.50
Purchase #6	$56.56	5.359%	$59.5911	$59.59	$59.60	$59.60
Purchase #7	$76.87	5.494%	$81.0932	$81.09	$81.10	$81.10
7 purchase totals =	$954.37		$1,051.2118	$1,051.21	$1,051.25	$1,051.20