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	$200.75	3.824%	$208.4267	$208.43	$208.45	$208.40
Purchase #2	$215.39	6.141%	$228.6171	$228.62	$228.60	$228.60
Purchase #3	$78.71	13.659%	$89.461	$89.46	$89.45	$89.50
Purchase #4	$109.32	6.207%	$116.1055	$116.11	$116.10	$116.10
Purchase #5	$116.94	12.231%	$131.2429	$131.24	$131.25	$131.20
Purchase #6	$63.31	12.684%	$71.3402	$71.34	$71.35	$71.30
Purchase #7	$58.77	7.386%	$63.1108	$63.11	$63.10	$63.10
7 purchase totals =	$843.19		$908.3042	$908.31	$908.30	$908.20