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	$235.71	5.265%	$248.1201	$248.12	$248.10	$248.10
Purchase #2	$35.60	7.850%	$38.3946	$38.39	$38.40	$38.40
Purchase #3	$233.80	9.169%	$255.2371	$255.24	$255.25	$255.20
Purchase #4	$227.53	12.535%	$256.0509	$256.05	$256.05	$256.10
Purchase #5	$104.41	7.600%	$112.3452	$112.35	$112.35	$112.30
Purchase #6	$27.71	13.477%	$31.4445	$31.44	$31.45	$31.40
Purchase #7	$238.53	12.107%	$267.4088	$267.41	$267.40	$267.40
7 purchase totals =	$1,103.29		$1,209.0012	$1,209.00	$1,209.00	$1,208.90