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	$157.34	7.792%	$169.5999	$169.60	$169.60	$169.60
Purchase #2	$177.40	10.660%	$196.3108	$196.31	$196.30	$196.30
Purchase #3	$222.78	3.268%	$230.0605	$230.06	$230.05	$230.10
Purchase #4	$58.30	10.770%	$64.5789	$64.58	$64.60	$64.60
Purchase #5	$202.35	11.219%	$225.0516	$225.05	$225.05	$225.10
Purchase #6	$82.30	8.486%	$89.284	$89.28	$89.30	$89.30
Purchase #7	$11.37	7.700%	$12.2455	$12.25	$12.25	$12.20
7 purchase totals =	$911.84		$987.1312	$987.13	$987.15	$987.20