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	$130.53	5.651%	$137.9063	$137.91	$137.90	$137.90
Purchase #2	$35.91	8.458%	$38.9473	$38.95	$38.95	$38.90
Purchase #3	$62.53	4.387%	$65.2732	$65.27	$65.25	$65.30
Purchase #4	$37.65	12.268%	$42.2689	$42.27	$42.25	$42.30
Purchase #5	$127.97	13.296%	$144.9849	$144.98	$145.00	$145.00
Purchase #6	$103.57	5.540%	$109.3078	$109.31	$109.30	$109.30
Purchase #7	$102.92	12.670%	$115.96	$115.96	$115.95	$116.00
7 purchase totals =	$601.08		$654.6484	$654.65	$654.60	$654.70