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	$208.54	3.486%	$215.8097	$215.81	$215.80	$215.80
Purchase #2	$76.96	12.259%	$86.3945	$86.39	$86.40	$86.40
Purchase #3	$175.81	10.604%	$194.4529	$194.45	$194.45	$194.50
Purchase #4	$62.39	3.173%	$64.3696	$64.37	$64.35	$64.40
Purchase #5	$34.67	13.380%	$39.3088	$39.31	$39.30	$39.30
Purchase #6	$225.25	8.564%	$244.5404	$244.54	$244.55	$244.50
Purchase #7	$228.43	5.712%	$241.4779	$241.48	$241.50	$241.50
7 purchase totals =	$1,012.05		$1,086.3538	$1,086.35	$1,086.35	$1,086.40