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	$128.94	10.582%	$142.5844	$142.58	$142.60	$142.60
Purchase #2	$140.30	3.479%	$145.181	$145.18	$145.20	$145.20
Purchase #3	$214.70	12.439%	$241.4065	$241.41	$241.40	$241.40
Purchase #4	$142.68	13.807%	$162.3798	$162.38	$162.40	$162.40
Purchase #5	$86.37	3.194%	$89.1287	$89.13	$89.15	$89.10
Purchase #6	$165.41	13.138%	$187.1416	$187.14	$187.15	$187.10
Purchase #7	$114.33	13.856%	$130.1716	$130.17	$130.15	$130.20
7 purchase totals =	$992.73		$1,097.9936	$1,097.99	$1,098.05	$1,098.00