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	$244.59	6.264%	$259.9111	$259.91	$259.90	$259.90
Purchase #2	$173.26	12.686%	$195.2398	$195.24	$195.25	$195.20
Purchase #3	$103.26	7.558%	$111.0644	$111.06	$111.05	$111.10
Purchase #4	$127.54	4.638%	$133.4553	$133.46	$133.45	$133.50
Purchase #5	$52.83	13.505%	$59.9647	$59.96	$59.95	$60.00
Purchase #6	$108.77	7.210%	$116.6123	$116.61	$116.60	$116.60
Purchase #7	$70.62	4.698%	$73.9377	$73.94	$73.95	$73.90
7 purchase totals =	$880.87		$950.1853	$950.18	$950.15	$950.20