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	$202.79	7.151%	$217.2915	$217.29	$217.30	$217.30
Purchase #2	$48.59	11.453%	$54.155	$54.16	$54.15	$54.20
Purchase #3	$69.49	9.489%	$76.0839	$76.08	$76.10	$76.10
Purchase #4	$181.35	13.350%	$205.5602	$205.56	$205.55	$205.60
Purchase #5	$172.47	3.457%	$178.4323	$178.43	$178.45	$178.40
Purchase #6	$102.68	13.343%	$116.3806	$116.38	$116.40	$116.40
Purchase #7	$148.74	13.213%	$168.393	$168.39	$168.40	$168.40
7 purchase totals =	$926.11		$1,016.2965	$1,016.29	$1,016.35	$1,016.40