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	$112.43	3.286%	$116.1244	$116.12	$116.10	$116.10
Purchase #2	$243.91	12.780%	$275.0817	$275.08	$275.10	$275.10
Purchase #3	$37.56	4.660%	$39.3103	$39.31	$39.30	$39.30
Purchase #4	$162.26	9.787%	$178.1404	$178.14	$178.15	$178.10
Purchase #5	$169.81	12.839%	$191.6119	$191.61	$191.60	$191.60
Purchase #6	$115.82	13.628%	$131.6039	$131.60	$131.60	$131.60
Purchase #7	$67.73	12.668%	$76.31	$76.31	$76.30	$76.30
7 purchase totals =	$909.52		$1,008.1826	$1,008.17	$1,008.15	$1,008.10