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	$245.32	6.740%	$261.8546	$261.85	$261.85	$261.90
Purchase #2	$45.75	7.789%	$49.3135	$49.31	$49.30	$49.30
Purchase #3	$109.29	6.570%	$116.4704	$116.47	$116.45	$116.50
Purchase #4	$162.77	11.258%	$181.0946	$181.09	$181.10	$181.10
Purchase #5	$189.83	4.602%	$198.566	$198.57	$198.55	$198.60
Purchase #6	$157.56	9.487%	$172.5077	$172.51	$172.50	$172.50
Purchase #7	$194.72	10.592%	$215.3447	$215.34	$215.35	$215.30
7 purchase totals =	$1,105.24		$1,195.1515	$1,195.14	$1,195.10	$1,195.20