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	$225.54	4.145%	$234.8886	$234.89	$234.90	$234.90
Purchase #2	$119.62	9.704%	$131.2279	$131.23	$131.25	$131.20
Purchase #3	$90.88	4.107%	$94.6124	$94.61	$94.60	$94.60
Purchase #4	$183.55	7.612%	$197.5218	$197.52	$197.50	$197.50
Purchase #5	$102.55	13.418%	$116.3102	$116.31	$116.30	$116.30
Purchase #6	$156.82	11.396%	$174.6912	$174.69	$174.70	$174.70
Purchase #7	$81.51	8.108%	$88.1188	$88.12	$88.10	$88.10
7 purchase totals =	$960.47		$1,037.3709	$1,037.37	$1,037.35	$1,037.30