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	$111.96	3.682%	$116.0824	$116.08	$116.10	$116.10
Purchase #2	$198.82	10.330%	$219.3581	$219.36	$219.35	$219.40
Purchase #3	$143.76	7.397%	$154.3939	$154.39	$154.40	$154.40
Purchase #4	$64.27	5.635%	$67.8916	$67.89	$67.90	$67.90
Purchase #5	$11.60	3.760%	$12.0362	$12.04	$12.05	$12.00
Purchase #6	$112.25	6.803%	$119.8864	$119.89	$119.90	$119.90
Purchase #7	$187.51	9.264%	$204.8809	$204.88	$204.90	$204.90
7 purchase totals =	$830.17		$894.5295	$894.53	$894.60	$894.60