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	$84.29	8.260%	$91.2524	$91.25	$91.25	$91.30
Purchase #2	$214.91	12.132%	$240.9829	$240.98	$241.00	$241.00
Purchase #3	$127.54	4.587%	$133.3903	$133.39	$133.40	$133.40
Purchase #4	$68.61	5.435%	$72.339	$72.34	$72.35	$72.30
Purchase #5	$87.60	12.429%	$98.4878	$98.49	$98.50	$98.50
Purchase #6	$228.84	12.246%	$256.8637	$256.86	$256.85	$256.90
Purchase #7	$243.81	5.621%	$257.5146	$257.51	$257.50	$257.50
7 purchase totals =	$1,055.60		$1,150.8307	$1,150.82	$1,150.85	$1,150.90