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	$131.96	4.233%	$137.5459	$137.55	$137.55	$137.50
Purchase #2	$226.97	5.301%	$239.0017	$239.00	$239.00	$239.00
Purchase #3	$119.39	6.798%	$127.5061	$127.51	$127.50	$127.50
Purchase #4	$36.29	11.108%	$40.3211	$40.32	$40.30	$40.30
Purchase #5	$211.43	7.725%	$227.763	$227.76	$227.75	$227.80
Purchase #6	$126.48	3.160%	$130.4768	$130.48	$130.50	$130.50
Purchase #7	$149.29	4.484%	$155.9842	$155.98	$156.00	$156.00
7 purchase totals =	$1,001.81		$1,058.5988	$1,058.60	$1,058.60	$1,058.60