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	$77.53	11.294%	$86.2862	$86.29	$86.30	$86.30
Purchase #2	$196.67	12.441%	$221.1377	$221.14	$221.15	$221.10
Purchase #3	$237.52	4.661%	$248.5908	$248.59	$248.60	$248.60
Purchase #4	$139.45	8.391%	$151.1512	$151.15	$151.15	$151.20
Purchase #5	$121.32	11.212%	$134.9224	$134.92	$134.90	$134.90
Purchase #6	$119.79	9.431%	$131.0874	$131.09	$131.10	$131.10
Purchase #7	$75.64	13.442%	$85.8075	$85.81	$85.80	$85.80
7 purchase totals =	$967.92		$1,058.9832	$1,058.99	$1,059.00	$1,059.00