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	$217.96	3.864%	$226.382	$226.38	$226.40	$226.40
Purchase #2	$138.48	5.631%	$146.2778	$146.28	$146.30	$146.30
Purchase #3	$161.42	3.130%	$166.4724	$166.47	$166.45	$166.50
Purchase #4	$47.33	10.337%	$52.2225	$52.22	$52.20	$52.20
Purchase #5	$180.46	13.493%	$204.8095	$204.81	$204.80	$204.80
Purchase #6	$37.44	13.219%	$42.3892	$42.39	$42.40	$42.40
Purchase #7	$237.37	4.618%	$248.3317	$248.33	$248.35	$248.30
7 purchase totals =	$1,020.46		$1,086.8851	$1,086.88	$1,086.90	$1,086.90