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	$212.88	13.498%	$241.6145	$241.61	$241.60	$241.60
Purchase #2	$83.84	6.408%	$89.2125	$89.21	$89.20	$89.20
Purchase #3	$219.88	5.245%	$231.4127	$231.41	$231.40	$231.40
Purchase #4	$218.83	6.666%	$233.4172	$233.42	$233.40	$233.40
Purchase #5	$239.28	9.108%	$261.0736	$261.07	$261.05	$261.10
Purchase #6	$13.56	13.307%	$15.3644	$15.36	$15.35	$15.40
Purchase #7	$46.70	10.424%	$51.568	$51.57	$51.55	$51.60
7 purchase totals =	$1,034.97		$1,123.6629	$1,123.65	$1,123.55	$1,123.70