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	$6.81	7.245%	$7.3034	$7.30	$7.30	$7.30
Purchase #2	$187.61	4.694%	$196.4164	$196.42	$196.40	$196.40
Purchase #3	$114.64	4.591%	$119.9031	$119.90	$119.90	$119.90
Purchase #4	$216.42	10.360%	$238.8411	$238.84	$238.85	$238.80
Purchase #5	$206.55	4.856%	$216.5801	$216.58	$216.60	$216.60
Purchase #6	$124.86	7.547%	$134.2832	$134.28	$134.30	$134.30
Purchase #7	$73.52	11.587%	$82.0388	$82.04	$82.05	$82.00
7 purchase totals =	$930.41		$995.3661	$995.36	$995.40	$995.30