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	$164.49	13.349%	$186.4478	$186.45	$186.45	$186.40
Purchase #2	$198.85	3.515%	$205.8396	$205.84	$205.85	$205.80
Purchase #3	$102.59	6.116%	$108.8644	$108.86	$108.85	$108.90
Purchase #4	$214.25	4.699%	$224.3176	$224.32	$224.30	$224.30
Purchase #5	$218.63	13.626%	$248.4205	$248.42	$248.40	$248.40
Purchase #6	$94.75	5.397%	$99.8637	$99.86	$99.85	$99.90
Purchase #7	$47.77	12.507%	$53.7446	$53.74	$53.75	$53.70
7 purchase totals =	$1,041.33		$1,127.4982	$1,127.49	$1,127.45	$1,127.40