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	$61.93	9.162%	$67.604	$67.60	$67.60	$67.60
Purchase #2	$63.88	8.863%	$69.5417	$69.54	$69.55	$69.50
Purchase #3	$170.61	8.613%	$185.3046	$185.30	$185.30	$185.30
Purchase #4	$100.81	3.229%	$104.0652	$104.07	$104.05	$104.10
Purchase #5	$51.90	10.822%	$57.5166	$57.52	$57.50	$57.50
Purchase #6	$54.45	9.835%	$59.8052	$59.81	$59.80	$59.80
Purchase #7	$153.46	8.385%	$166.3276	$166.33	$166.35	$166.30
7 purchase totals =	$657.04		$710.1649	$710.17	$710.15	$710.10