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	$240.26	3.690%	$249.1256	$249.13	$249.15	$249.10
Purchase #2	$30.90	6.385%	$32.873	$32.87	$32.85	$32.90
Purchase #3	$99.51	10.484%	$109.9426	$109.94	$109.95	$109.90
Purchase #4	$161.50	7.177%	$173.0909	$173.09	$173.10	$173.10
Purchase #5	$179.29	3.471%	$185.5132	$185.51	$185.50	$185.50
Purchase #6	$126.52	3.225%	$130.6003	$130.60	$130.60	$130.60
Purchase #7	$51.94	12.458%	$58.4107	$58.41	$58.40	$58.40
7 purchase totals =	$889.92		$939.5563	$939.55	$939.55	$939.50