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	$133.86	9.599%	$146.7092	$146.71	$146.70	$146.70
Purchase #2	$38.76	12.331%	$43.5395	$43.54	$43.55	$43.50
Purchase #3	$111.98	5.336%	$117.9553	$117.96	$117.95	$118.00
Purchase #4	$179.54	6.416%	$191.0593	$191.06	$191.05	$191.10
Purchase #5	$120.74	13.688%	$137.2669	$137.27	$137.25	$137.30
Purchase #6	$143.46	12.647%	$161.6034	$161.60	$161.60	$161.60
Purchase #7	$193.31	12.708%	$217.8758	$217.88	$217.90	$217.90
7 purchase totals =	$921.65		$1,016.0094	$1,016.02	$1,016.00	$1,016.10