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	$103.86	7.473%	$111.6215	$111.62	$111.60	$111.60
Purchase #2	$92.85	9.838%	$101.9846	$101.98	$102.00	$102.00
Purchase #3	$104.92	13.525%	$119.1104	$119.11	$119.10	$119.10
Purchase #4	$125.95	12.405%	$141.5741	$141.57	$141.55	$141.60
Purchase #5	$196.43	7.215%	$210.6024	$210.60	$210.60	$210.60
Purchase #6	$187.72	13.524%	$213.1073	$213.11	$213.10	$213.10
Purchase #7	$48.47	13.823%	$55.17	$55.17	$55.15	$55.20
7 purchase totals =	$860.20		$953.1703	$953.16	$953.10	$953.20