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	$133.51	11.530%	$148.9037	$148.90	$148.90	$148.90
Purchase #2	$5.73	13.328%	$6.4937	$6.49	$6.50	$6.50
Purchase #3	$74.48	9.175%	$81.3135	$81.31	$81.30	$81.30
Purchase #4	$142.73	7.609%	$153.5903	$153.59	$153.60	$153.60
Purchase #5	$237.58	4.784%	$248.9458	$248.95	$248.95	$248.90
Purchase #6	$101.75	3.615%	$105.4283	$105.43	$105.45	$105.40
Purchase #7	$91.79	9.219%	$100.2521	$100.25	$100.25	$100.30
7 purchase totals =	$787.57		$844.9274	$844.92	$844.95	$844.90