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	$164.39	5.248%	$173.0172	$173.02	$173.00	$173.00
Purchase #2	$87.77	12.286%	$98.5534	$98.55	$98.55	$98.60
Purchase #3	$192.40	3.371%	$198.8858	$198.89	$198.90	$198.90
Purchase #4	$178.28	4.282%	$185.9139	$185.91	$185.90	$185.90
Purchase #5	$139.89	7.631%	$150.565	$150.57	$150.55	$150.60
Purchase #6	$28.48	13.603%	$32.3541	$32.35	$32.35	$32.40
Purchase #7	$62.32	8.264%	$67.4701	$67.47	$67.45	$67.50
7 purchase totals =	$853.53		$906.7595	$906.76	$906.70	$906.90