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	$158.48	3.711%	$164.3612	$164.36	$164.35	$164.40
Purchase #2	$163.90	6.695%	$174.8731	$174.87	$174.85	$174.90
Purchase #3	$103.88	5.744%	$109.8469	$109.85	$109.85	$109.80
Purchase #4	$111.38	4.342%	$116.2161	$116.22	$116.20	$116.20
Purchase #5	$231.78	7.258%	$248.6026	$248.60	$248.60	$248.60
Purchase #6	$71.34	13.632%	$81.0651	$81.07	$81.05	$81.10
Purchase #7	$108.69	11.634%	$121.335	$121.34	$121.35	$121.30
7 purchase totals =	$949.45		$1,016.3000	$1,016.31	$1,016.25	$1,016.30