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	$64.31	8.835%	$69.9918	$69.99	$70.00	$70.00
Purchase #2	$102.28	11.662%	$114.2079	$114.21	$114.20	$114.20
Purchase #3	$35.68	13.389%	$40.4572	$40.46	$40.45	$40.50
Purchase #4	$238.36	8.571%	$258.7898	$258.79	$258.80	$258.80
Purchase #5	$246.93	6.606%	$263.2422	$263.24	$263.25	$263.20
Purchase #6	$158.43	13.627%	$180.0193	$180.02	$180.00	$180.00
Purchase #7	$83.37	7.176%	$89.3526	$89.35	$89.35	$89.40
7 purchase totals =	$929.36		$1,016.0608	$1,016.06	$1,016.05	$1,016.10