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	$140.95	4.364%	$147.1011	$147.10	$147.10	$147.10
Purchase #2	$109.40	6.190%	$116.1719	$116.17	$116.15	$116.20
Purchase #3	$145.26	9.356%	$158.8505	$158.85	$158.85	$158.90
Purchase #4	$198.31	5.199%	$208.6201	$208.62	$208.60	$208.60
Purchase #5	$244.58	13.812%	$278.3614	$278.36	$278.35	$278.40
Purchase #6	$10.90	4.183%	$11.3559	$11.36	$11.35	$11.40
Purchase #7	$148.95	11.355%	$165.8633	$165.86	$165.85	$165.90
7 purchase totals =	$998.35		$1,086.3242	$1,086.32	$1,086.25	$1,086.50