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	$118.86	3.685%	$123.24	$123.24	$123.25	$123.20
Purchase #2	$110.87	8.411%	$120.1953	$120.20	$120.20	$120.20
Purchase #3	$106.89	4.398%	$111.591	$111.59	$111.60	$111.60
Purchase #4	$232.77	3.588%	$241.1218	$241.12	$241.10	$241.10
Purchase #5	$204.51	9.249%	$223.4251	$223.43	$223.45	$223.40
Purchase #6	$152.46	8.438%	$165.3246	$165.32	$165.30	$165.30
Purchase #7	$41.31	4.724%	$43.2615	$43.26	$43.25	$43.30
7 purchase totals =	$967.67		$1,028.1593	$1,028.16	$1,028.15	$1,028.10