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	$48.41	8.264%	$52.4106	$52.41	$52.40	$52.40
Purchase #2	$240.62	5.773%	$254.511	$254.51	$254.50	$254.50
Purchase #3	$127.37	3.378%	$131.6726	$131.67	$131.65	$131.70
Purchase #4	$134.35	3.866%	$139.544	$139.54	$139.55	$139.50
Purchase #5	$160.83	4.699%	$168.3874	$168.39	$168.40	$168.40
Purchase #6	$216.79	7.132%	$232.2515	$232.25	$232.25	$232.30
Purchase #7	$75.78	12.455%	$85.2184	$85.22	$85.20	$85.20
7 purchase totals =	$1,004.15		$1,063.9955	$1,063.99	$1,063.95	$1,064.00