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	$84.72	8.321%	$91.7696	$91.77	$91.75	$91.80
Purchase #2	$197.87	5.318%	$208.3927	$208.39	$208.40	$208.40
Purchase #3	$212.28	7.579%	$228.3687	$228.37	$228.35	$228.40
Purchase #4	$169.31	13.361%	$191.9315	$191.93	$191.95	$191.90
Purchase #5	$62.43	8.233%	$67.5699	$67.57	$67.55	$67.60
Purchase #6	$226.31	3.823%	$234.9618	$234.96	$234.95	$235.00
Purchase #7	$96.39	8.387%	$104.4742	$104.47	$104.45	$104.50
7 purchase totals =	$1,049.31		$1,127.4684	$1,127.46	$1,127.40	$1,127.60